IMAC w/macOS Catalina running slow and freezing

What could be causing it to run so slow?

"AV for MAC"

Get rid of it. Rule 1 of Macs is don't install junk.

it was recommended that I protect my MAC.

Effective defenses against malware and other rhreats - Apple Community

There is no reason to ever run any "cleaning", "optimizing", "speed-up" or anti-virus apps on your Mac.  This user tip describes what you need to know and do to protect your Mac: Effective defenses against malware and other threats - Apple Community   

Download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

Copy the report

and use the Add Text button to include the report in your reply. How to use the Add Text Feature When Posting Large Amounts of Text, i.e. an Etrecheck Report

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Then we can examine the report and see if we can determine what might be causing the problem.

You've installed what most of the experienced users who contribute to these forums consider akin to malware: CleanMyMac.

There is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus or security apps on your Mac.  This user tip describes what you need to know and do to protect your Mac: Effective defenses against malware and other threats - Apple Community.  The TotalAV falls into this category also.

Uninstall both according to the developer's instructions:

 How to uninstall CleanMyMac X

Uninstall in Mac OSX - TotalAV

You can check to see if you've removed all of the supporting files by downloading and running Find Any File to search for any files with the application's name  and the developer's name in the file name.  For example for the indicated software you'd do the following searches: 

1 - Name contains cleanmymac

2 - Name contains macpaw

3 - Name contains totalAV

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.  

ALSO, you have some adware installed. Download and run the free version of Malwarebytes. It was developed by a long time contributor to these forums and a highly respected member of the computer security community. 

Be aware that the iMac model you have was the slowest iMac offered by Apple at the time of purchase: 8 GB of RAM and a 5400 rpm hard drive. With that in mind it would help performance to limit what you have in your User Login Items to launch at boot time. Open apps when needed and close when done. Don't have apps running in the background full time. Also reboot at least 2-3 times a week to clear out temporary system, cache and swap files.

"CleanMyMac" claims another victim.