I have a Kenmore 20 yr old electric dryer. It will start fine for first load. But when Dryer is stopped to check clothes it will not start again. When the start button is pushed a loud 'buzzing' or 'humming' is heard and the drum does not turn. The 'buzzing' or 'humming' is only heard while the start button is being pushed. Once the dryer has cooled down again it will start fine. Any ideas what is wrong???