Mac is starting to run very slow and the fan kicks on high.

DO NOT install CleanMyMac, know by senior contributors here as "Brick My Mac". it is essentially paid malware.

Your Mac does not accumulate filth, and does not need to be cleaned by any third-party junk ware to maintain its speed.

Consider running respected Discovery Utility Etrecheck, and posting its report.

https://etrecheck.com/en/index.html

.

For. 25 years, the macOS has featured elegant, automated self-maintenance routines that do all needed housekeeping, even defragging, so you don't have to buy scammy utilities that too often cause more issues they fix. Those unneeded utilities too often competes with the elegance you paid Apple to build into the OS, hurting performance and stability.

The self-maintenance routines run in the small hours of the morning when most people are not using their computers. If the computer is off (as opposed to sleeping) the routines run in the next idea time after startup.