Its possibly your thermal fuse. On gas dryers they can run but not heat when the thermal fuse goes out. On electric dryers the dryer won't run at all when the thermal fuse goes out.
Pull your dryer away from the wall, then Unplug it, then take off the back access panel and you can ohm it for continuity, or take the wires off and jump it, use alligator clips or electrical tape to tape them together, just for testing, DON'T RUN IT THAT WAY FOR A CYCLE IF IT WORKS!
The main reason the thermal fuse blows is air flow restrictions in your exhaust hose that goes to the outside of your home, lint build-up over the years effects the air flow, also go outside and check your dryer vent, that can clog up too.