I've narrowed it down to a few possibilites that it could be:
-Faulty bulb (I would guess this is not the problem. The bulb should just die, and not go on & off intermittently right?)
I seen many bulbs go intermittent like you described. Could be the bulb base isn't seating well in the socket or the bulb is at fault. I would start with that.
Regards, Dan