Your post leaves lots to the imagination. What does trying to start
mean? Does it start, then quit when you release the start switch? Or
does it groan and never completely get going when you push the switch?
For the former...look at the evenheat control in the control panel.
For the latter...groaning during start indicates a bad motor. Replace
btw, if only a belt is broken, the dryer will either start and not turn
drum (if there is no belt switch), or it will not start at all (if
there is a belt switch).