when cool, dryer motor will turn on when start button pushed. Drum rotates and element gets hot. after a few minutes there is a slight burning odor near the motor area. following turning off the dryer and waiting a few minutes,the start button is oushed and there is a loud humming noise,like the motor is dragging, but it will not start. the dryer heating element seems to heat up very rapidly.any and all suggestions would be very helpful. thanks,Bob