My iMac will shut down randomly. After it shuts down I feel it to see how hot it is. It happens to be pretty hot but I never hear the fans going. This has only happened about 7 times in the past 3 months. My iMac is on a desk pushed up against a wall with a shelf connected to the desk. I'm fairly certain that it might have something to do with the fact that the air is circulating but I'd feel better if I got a second opinion on the situation.