What program are you in when that happens, does it happen in the same program each time? What do you run that's open all the time? Did you do a virus/spyware scan? Maybe heat related, open up the case and clean out the dust (don't use a vaccum, get some compressed air or use a vaccum on exhaust. Using a vaccum puts you at risk of popping off something critical from the motherboard and can also cause static discharge.
Unless you are having a hardware issue (possible), most straight-forward way to try to fix this is to backup your data, and re-install Windows, see if that fixes the issue.