Fridgidaire gas stove oven glow lights up but oven doesn't come on sometimes then I smell gas, other times it comes right on with no problems

This is a common problem that happens when the oven gas control valve is sticking. This can be caused by a weak hot surface igniter or a defective gas control valve. One thing that you can try(be very careful doing this) is to give the gas control valve a light tap with something hard like a wrench when the oven is turned on,igniter is glowing but the burner is not on. You will need to remove the broiler/storage drawer at the bottom of the oven. Once you pull the drawer out you should see the gas control valve at the back of the range. Try turning on the oven and lightly tapping the valve housing. This may loosen up any debris inside the control valve housing that might be causing the problem. If the oven burner comes on then try completely turning the oven on and back of several times. And when I say completely I mean turn it on after the igniter is not glowing and burner has shut off. This works about 30% of the time. If the burner control valve stick after trying this procedure then it could be the control valve and/or the hot surface igniter defective. The hot surface igniter would need to be disconnected from it's harness and tested with an OHM meter. Most igniters should have a 500 to 700 OHM reading. If you get a reading that is way off then the igniter is defective and replace it. If the igniter tests good then the gas control valve is suspect and replace it. Most appliance parts retailers will test your igniter for free. When the igniter is on it should glow very brightly. If it is dim then that is a sure sign it is bad.