I have a 2001 Saturn SL2 that is having a problem with one of its headlights. When I turn on the headlights, frequently one is not lighting. If I go to the front and give the lens a quick knock, it turns on and stays on until I turn the headlights off. It doesn't flicker or show signs of a loose connection. I have cleaned the connector and that hasn't helped. I'm out of ideas at this point and hope someone can suggest a next step.
My suggestion is that the filament inside of the bulb is loose. When you rap on it, it reconnect briefly, which lights the bulb. It will continue to do this until it completely burns out. This will probably require a replacement bulb to fix.