Monterey 12.5.1

1 - Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal.

2 - Does the issue present in this mode ?

Skip point one and two above , if you wish to

3 - Sometimes a Safe Boot followed by a Normal Boot will just put things right.

4 - If not - there could be something in the main User Account playing up. To further isolate this - Set up users, guests, and groups on Mac. Then log out of the Main User account and log into the dummy account and test again if the issue persists.

5 - If the issue is present in the dummy account - then, this appears to be a System Wide issue on the computer.

Understand, we are all working Remotely from all around the world. 

Therefore, we do not have the On-Hands experience the User ( you ) has with this computer.

The next best thing for us to having a semi - actual On-Hand experience on this computer is to follow the steps below

Download the Application Etrecheck directly from the Developer.

The application is free or paid from added features. 

It will take a Snap Shot -  both the hardware and software.

 The Report will Not Reveal Any Personal Information. 

Post back the Full Report - copy and paste - using the Additional Text Icon ( 3rd Icon to last )

We can have a look at the report for possible issues and may have possible suggestions to resolve the issues.

First, there is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.  

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is designed solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  

So as already recommended uninstall CleanMyMac and AVG according to the developer;s instructions.

You can check to see if you've removed all of the supporting files by downloading and running the shareware app Find Any File to search for any files with the application's or the developer's name in the file name.  For the two apps mentioned you'd do the following search(es): 

1 - Name contains cleanmymac

2 - Name contains macpaw

3 - Name contains avg

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  

Problem: Computer is too slow

Description: After loading Monterey 12.5.1 my iMac slowed down considerably and some apps just don’t work. 

Major Issues:

Q - Hard drive is too slow - The hard drive in this computer is too slow.

A - this will be covered later in this reply

Q - Security updates disabled - Security updates are disabled. This computer is at risk of malware infection.

A - Personal choice but do suggest running with it On

Q - Apple security disabled - Apple security software is disabled. This computer is at risk of malware infection.

A - Personal choice but do suggest running with it On

Q - More than one antivirus app - This computer has multiple antivirus apps installed.

A - Will cover this later run this reply and in detail

Q - Unsigned files - There are unsigned software files installed. These files could be old, incompatible, and cause problems. They should be reviewed.

A - Self explanatory and suggest review the this party software of update / upgrades or outright replacements to bring them in line with Monterey 

Q - System modifications - There are a large number of system modifications running in the background.

A - Running the computer with the operating system many modifications, be they intended or otherwise,  will have consequences which maybe what the computer is experiencing now

Hardware Information:

  iMac (Retina 5K, 27-inch, 2017)

Drives:

Q -  disk0 - APPLE SSD SM0032L 28.00 GB (Solid State - TRIM: Yes) 

  Internal PCI-Express 8.0 GT/s x2 NVM Express

Q - disk1 - APPLE HDD ST1000DM003 1.00 TB (Mechanical - 7200 RPM) 

 A - Fusion Drives were good in their day for additional storage capacity but starting around Catalina and especially in Big Sur and again in Monterey, the drive will struggle to perform under the damages of both the needs of the user and in Monterey. The performance of the computer will never reach the performance  levels if it were an All SSD configuration.

A - Should the user wish to extended the life of the computer and gain the performance expectations - invest in a good Enclosure and a good SSD with the drive capacities needs for your needs. Install  Monterey Directly to the external configuration and set the external drive as the Boot-up Drive. The performance gains will be  day and night gains. A good and suggested source would be www.owc.com and they have have specific units to match this specific computer 

Security:

Q - Antivirus software: AVG, CleanMyMac, and Malwarebytes

A - There are no known Windows-like Viruses in the wild that self replicate and affect macOS, because of the underling UNIX  Foundation and Permission Limitation. 

Additionally, and specific to Big Sur macOS 11 and Monterey macOS 12, the Operating System resides in a Sealed and Read Only Volume that can not be opened by the User and protects against from “ Bad Actor “ Software.

The Only thing this Antivirus software is protecting is the Bank Account of the Developers and for zero return to the User aside from the problems this software creates.

AntiVirus Developers purposefully Market their product to create a “ Fear Factor “. In so doing, creating a False Need for their Product.

A - Any Third Party Applications that will interfere with the normal operation of the OS,  is an invitation for disaster and comprising the Operating System

Certain Applications maybe available on the Apple Apps Store - this only means the Developer is prepared to pay Apple a portion on each sale. What the Application may do to the computer is up to the User to check this out before purchase

Any of the below should be removed as per Developers Instructions

This will include CleanMyMac 

Sophos Av Software

Intego AntiVirus, McAfee, MacKeeper, Avast AntiVirus

Ad Guard, Webroot , ESET , Kaspersky Antivirus. Anti virus

Suggest reading some of the posting specific to CleanMyMac aka BrickMyMac and AVG software and arrive at your own conclusions

As for Malwarebytes - it fine to keep but not running all the time. It just consumes Resources and CPU power for little return

Q - /Library/Extensions [Not Loaded] CUDA.kext - com.nvidia.CUDA (1.1.0)

A - This is outside of my expertise, so will only say, running a non native apple kernel extension for video can be a contributing factor in the overall performance of this machine

If you are referring to /Library/Extensions [Not Loaded] CUDA.kext - com.nvidia.CUDA (1.1.0) that would have had to be Purposefully installed by the User and possibly requiring Disabling SIP ( System Integrity Protection ) to allow this kernel extension to be installed.

Thank you for the Report.

I will dissect it, in detail,  and get back to you shortly