My dryer only turns itself off when in a heat mode... not fluff. I don't think it is the motor. Any suggestions?

It sounds like it is overheating and the thermal cutout is shutting it off. I would pull the dryer out from the wall and take a look at the vent pipe and make sure it is clear of lint. Look back into the dryer and forward down the pipe towards the outside--make it as clean as possible. This lint can catch fire.

Best of luck,
WallyH