[Daynarr]

Narf, there are at least 2 processors in your PC that can cause this - GPU and CPU. You need to make sure that both of them are not overheating (sounds like the case). GPU tends to do the kind of thing you described so you need to check your graphic card if it overheats.

Also, don't forget to check for viruses. You can get Avast or AVG free versions to check your system properly (google for links).