To add to lemerise. Be sure to NOT let the fans spin up really fast when blowing them out with the compressed air. Very bad to do this. Can cause damage to the fan. Just place a finger on the fans to hold them in place while you blow them out.

How old is your Xbox? If you have had it for awhile, then it is possible that there is dust inside making it over heat. Like any electronic device over time they get dusty inside. Try cleaning it out and see if you are still getting this issue. Try this.