Dryer not heating

Dryer comes on Perfect for approximately four minutes then it sounds like gas gas shuts off indeed no heat. Heat wont come back until I leave shut off 5-10 minutes then it just same ole thing. I have noticed a periodic glow must be an ignitor when i try to increase time on dial after heat shuts off doesn’t work , only way it will restart is shut off and come back after again 5-10 minutes. I have checked vent ducting not the problem i also replaced the thermafuse and the thermastat. But now i think i getting closer to believing its somthing to do with gas because today i actually smelled gas outside where dryer vents. Questions thoughts ideas???