Usually it's the motor,there's an overload on the motor that shuts it down when it's to hot,when was the last time you cleaned out the dryer?there could be lint covering the motor,this will overheat it,clean out the duct that the lint filter slides into,blow out the vent line and vac the inside of the dryer where the motor is,next time send the model number and how old the dryer is,clean out the dryer and don't do one load after another and you can still get some life out of the dryer,if the dryer is old use it until it dies