I’m having some intermittent problems with the dryer. I took off the panel and the igniter starts the gas sometimes but not all the time. Then when i check the laundry the cloths are still damp and the flame is out. So I don’t get full heat to finish a full load of cloths. What do you thing is the problem? Relay? 
Any help will greatly appreciated.
It sounds like your coils may be bad. Check the coils and see if they test good. You can test the coils using a multi-meter. The two prong coil will read 1,000-1,300 ohms, and the three prong coil will read 1,300-1,400 ohms across prongs 1&2, and 500-600 ohms across prongs 1&3. Hope this helps.
AP3094251
Gas valve & igniter replacement parts for MAYTAG SDG5701AWW DRYER- GAS | AppliancePartsPros.com