My EtreCheck Report

It seems you are having Kernel Panics. Please see: If your Mac restarts and a message appears - Apple Support. (they are most likely due to CleanMyMac.)

Delete CleanMyMac. [Instructions] It is akin to malware.

Remove the orphan files. Their locations can be found at the bottom of your EtreCheck report.

You have a lot of Internet Plug-Ins. I would remove them. Their locations are /Library/Internet Plug-Ins/ and ~/Library/Internet Plug-Ins/ .

However, the main reason your iMac is slow is due to the 7200 RPM hard drive. If you use an external SSD and run macOS from that, it will make your Mac 10 to 30 times faster for storage. For more info, instructions, and what external SSD to buy, please read: How to Setup and Use an External SSD as y… - Apple Community.

You could also upgrade the RAM to 16GB. The external SSD is more important, but more RAM cannot hurt! Here are 16GB upgrade kits: 16GB OWC MEMORY UPGRADE KIT - MacSales.com (OWC) or Crucial 16GB Kit (2 x 8GB) SODIMM Memory for Mac - Crucial. Here are the upgrade instructions: Install memory in an iMac - Apple Support.

Cheers,

Jack

There is no EtreCheck report attached. Please post it following these instructions: How to use the Add Text Feature When Post… - Apple Community.

Also, let us know what is going on with your Mac.

Jack

Might do, if you could add the "this"...

You're welcome!