Memory exhaustion? Pull up task manager (press CTRL-SHIFT-ESC at the same time) and see what process is flying close to the wind and chewing all the resources. Maybe you have some programs in the startup section that do not need to be running all the time? How about viruses and malware? Hidden cryptominers?
Disk drive paging errors? Check the system log, and also drive parameters for spare blocks being consumed. Do a full disk check as indicated in previous posts. Check that your backup software is completing, and that backups are actually restorable by renaming a file and then attempting a restore from backup.
4Gb is a bare minimum for Windows 10 these days. Both the problems above can be postponed for a while by upgrading to more memory. Cheap performance boost. Most motherboards more than a few years old may not be able to support more. YMMV.
You check you CPU for heating issues. Did you check your graphic chip on the motherboard as well?
Is your monitor and PC plugged into the same power outlet? Not on different phases on the power? Is one on a UPS and the other not? Maybe ground loops?
Do you vacuum your equipment often? Dust buildup and spiders do not mix well with lectrickery...
If you do isolate the problem, it may be insightful to document it here for others, as often these issues are just left open on forums and nobody knows what the problem actually was and how it was remedied.