Try running it with the cover off and a large fan blowing on it. Also try to make sure it's in a cool area to begin with. If your problems go away, then yeah it's probably a heat problem and you can fix it accordingly (leave cover off, add more fans, relocate to cooler location, etc.). If it still has the same problem, I'd look at there being a different issue. I had a problem where my PC would keep crashing under heavy load, turned out to be a bad stick of ram.