Honestly, from what you have described it sounds to me like you're having hardware issues. Typically, (in my experience as a tech), heating (cpu fan, gpu fan), bad memory, video card failing. Less often, the PSU is insufficient (wattage, failing). Very rarely, the gpu and/or memory pins need cleaning (clean pencil erasor). How is the airflow?
BTW, Windows 11 is fine for gaming. If you're worried about privacy and ads, consider something like bloatynosy.
https://github.com/builtbybel/BloatyNosy