The dryer gas valve coils open the gas valves when the dryer is ready to heat up. If the dryer heats in the beginning, then stop heating when you come back the problem is usually the gas valve coils. If its not the gas valve coils it would be the High Limit Thermostat.
That’s because weak gas valve coils can sometimes open the valves when you first start the dryer, but when the burner cycles off and then try to re-light again, weak gas valve coils can’t open the valves again correctly, test run the dryer a couple of times. Replace the failed valve coils with an approved replacement part.
Some dryer models require removing the dryer drum to reach the valve coils. Here’s a repair guide that shows how to remove a dryer drum.
This process works for Kenmore, Whirlpool, Maytag, Amana, Roper, Crosley and Estate gas dryers with a lint screen located on the top. Although opening a dryer may differ, you can use the same basic repair steps to replace gas valve coils in Frigidaire, GE and Electrolux models.