I have a Maytag Atlantis mdg7400aww gas dryer. It has always worked great.. 3 Yrs old. She used it this morning fine then this evening no heat! It operates fine otherwise. Where should I start?

I have a Maytag Atlantis mdg7400aww gas dryer. It has always worked great.. 3 Yrs old. She used it this morning fine then this evening no heat!! It operates fine otherwise. Where should I start?
Tough call! Where do we start? Did you pay your gas bill? Could be an ignitor, could be a thermo-fuse if you have a long vent! Could be a thermostat or Hi-limit switch! Could be burner coils or a flame sensor! Very rarely it may be a timer! Did anyone accidentally switch it to Air Fluff? (Don't laugh, I've seen it more than once!)

It's just a matter of trying each step at a time!