Amana le3402w HD dryer buzzes when hit start?

My Amana le3402w will run sometimes then shuts off after 10-20 min. When I try to restart it just buzzes.
I am getting heat okay when it runs and have replaced rolleers and idler pulley. I suspect it is the motor bushings, but don't want to replace the motor if it could be a thermostat or switch problem.