Kenmore Gas Dryer model # 76912692 seris 900?

When you push the start button you get a loud humming for about 5 seconds and the dryer never starts to tumble. Try to start it again and you get no humming noise and it still does not start. Wait 5 minutes and we are back to the humming noise,which sounds like the motor. Any ideas? One stupid thing. The belt looks fryed in several spots but is still intact. Could it be so streched that it is not turning the drum or should I look elswere. After leaving the dryer overnight it started the next morning ran for 20 minutes then stopped and back to doing what is listed above.