It's just safety on your ballast. It takes a big burst of energy to light those bulbs. Sometimes if you turn it off and back on to fast it wont light. The glowing is warming up and a failed ignition. If you wait the ballast should try to relight the bulb without your help. When you unscrew and retry the bulb/ballast is just trying again to start.
What products are you using, and what are the circumstances of not starting the bulb? Is it at the begining of the day or after you turn it off and go in the room and try 2 turn it back on?