When I see one like this the first thing we do is to go ahead with a canned air cleaning and leave the cover off then see if it gets better. I find many owners don't keep up with the cleaning or never did the work.
This is not a temp issue since not all chips have temp sensors so it could be other than the CPU heat issue.
Since a clean install of the OS doesn't fix it, I suspect hardware so let's try the cheap usual fix first.
Next, let's dive under the hood with a WEB SPECCY. Read how at https://www.piriform.com/docs/speccy/using-speccy/publishing-a-speccy-profile-to-the-web
I would suggest a CHKDSK /F/R/X but not yet as a crash during this could wipe out the OS. If you feel you can reload, go ahead with the CHDKSK /F/R/X on all disks.