Your Xbox is overheating. You either need to call Microsoft and send it in for repairs or (if you can do this) you need to open it up and replace the x-clamps.
If he didn't get or see the 3 rings of death, then it's not overheated. Probably it's just that the 360 is mest up itself. Try fixing it yourself (you can search on youtube on how to do it) or just call Microsoft and send it over to repair.
-Chaldo