Recently the light on my automatic garage door opener (a Genie model, but I don't think that matters) started clicking on and off all the time. Didn't matter if the door was open or shut, the light would just randomly switch on or off.

I eventually tracked this down to the wall switch used to open and close the door. Replacing the switch fixed the problem. If the light on your automatic garage door keeps turning on and off, try disconnecting the wall switch to see if this stops the problem. If so, you'll need a new wall switch too.