My iMac is slow to start up

Please locate the uninstall instructions for CMM, it is malware and will only make your machine worse. Mac OS does not benefit from in ANY any of the following types of third party apps and all have the exact opposite effects users want!!!!

• Antivirus apps
• Cleaning apps
• Security apps
• VPN apps
• Maintenance apps

After you have uninstalled CMM then run a new EtreCheck report and look it over carefully for anything that says:

• CleanMyMac
• MacPaw

If it finds anything with these names that shows it did NOT fully uninstall. At that point stop and let us know.

I see you have Malwarebytes installed, that is OK and you should run it to see if it picks up any malware or adware you may have installed on the computer. Do this after you have ensure CMM is 100% eradicated from your system.

Due to the computers age, it is possible your HD may be having issues. To check it, download and run DriveDX and if ANY errors appear in the DriveDX reports then your HD is failing and needs to be replaced! If no errors appear, then take the computer to your local Apple Authorized Service Provider ( Apple Authorized Service Provider Locator (AASP) & Genius Appointment ) and have the computer checked over.

As you've already been alerted to you've installed what most of the experienced contributors here consider akin to malware: CleanMyMac.

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 documents describe what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community and Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support.  

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.  

Unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, they provide false security from a privacy standpoint.  Read these two articles: Public VPN's are anything but private and Security Risks: The Dangers of Using Free VPNs (eccu.edu)

So uninstall CMM 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 CMM software you'd do the following search(es): 

1 - Name contains cleanmymac

2 - Names contains macpaw

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.  

If you get warnings that the file can't be deleted because it is in use or used by another app boot into Safe Mode according to How to use safe mode on your Mac and delete from there.

Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.

It will help us get a good idea of what is causing your problem if you provide a report of your system, that way we do not have to play 20 questions with you. The report we are requesting does NOT provide any personal information and is extremely safe to use. Please navigate towww.Etrecheck.com and download the free version of EtreCheck. Once you have you downloaded the app and installed it, please run the report and save it. This report will help us get a good idea what has been installed on your system and help us be able to diagnose what may be wrong.

When you have your report, you can attach it when you reply to this message and we can then review it and help you determine what is needed to get your system running well again. 

For instructions on how to download your EtreCheck report and attach it to your reply to this message please click How to use the Add Text Feature When Post… - Apple Community It is helpful to us if you download the report to your Desktop.

Not much showing as a problem, other than rkaufmann87's CMM suggestion & running Drive DXs.

+1:)

Your welcome.

You're welcome. We're just passing on what we're learned here over the years. As they say: pass it forward. Good luck.