The timer could be the problem. To check this, turn the timer to a timed cycle say 30 minutes or so then time it. If in 30 minutes the timer hasn’t moved and the dryer is still on, the timer is bad and needs replacing. If in 30 minutes the dryer is off, the heating element is your problem
This is the most likely cause for some dryers timer not advancing. Some dryers have two heating elements and if one goes out the timer will not advance if you use it on an automatic cycle but you will still feel heat inside the tub. Replace the Heating Element.