THERE could be your problem!......the glow tube should not cycle on and off without igniting the flame.....if the glow tube is comming on, it's because the dryer is telling it that it requires more heat......once it gets red hot the gas valve is opened and the flame starts.....again, the igniter does not just cycle for the heck of it.......
I had this with a Maytag Neptune gas dryer......the glow tube would come on, but the valve would not always open.......using a screwdriver, once the glow tube got red, at the time the valve should have opened, I pushed on the solenoid, and it fired up....once I let go, the fire went out........replacing the solenoids fixed the issue......for a load of towels, it used to take up to 90 minutes to dry, now were back down to about 40 minutes......