Dryer motor windings or capacitor might be going bad check voltage at motor you should have (2) 120 readings at the motor one for start up and another for operation. Check motor with belt off unit and see if it works fine if so you may have a bad main bearing or rollers depending on the type of drum. If you don't get (2) 120 readings at motor suspect the main control board or maybe a shorting door switch? Check your wiring diagram and chase the trail of wiring make sure you got no shorts in the wiring also with continuity test. Good luck