When a dryer is not heating, it's usually a heating element replacement needed, not enought power in the outlet, one of the fuses are faulty, or control board is not working properly, or anything else. The best way is to check it on the spot.
This is the second most common issue with dryers. Usually it's a faulty fuse or thermostat. Also the control board may not work, no power in the outlet, heating element or motor are faulty, belt ripped off, no power coming to the unit
If the dryer is not stopping, usually it can be a control board (computer) is faulty. The replacement is required. However, there can be something else.
In this case, the dryer is clogged and the vent is clogge as well. An urgent cleaning of the dryer and vent is requried as there is a risk of fire.
The most of the time when the gas dryer is not heating enough, it means the coils are faulty and need to be replaced. However, there can be something else, including faulty computer or gas assembly, or there is no gas flow
Usually the reason is broken belt. Also, there can be issues with control board or rollers with pulley