1988 Cadillac Eldorado interior lighting problem

I have a 1988 Cadillac Eldorado. My interior lights randomly turn off and on only at night (all of them like the door handle is pushed). As of recent they have been turning on and off more rapidly. I slammed my passanger side door closed a week ago (thinking it was the door sensor) and it seemed to work for a day or two. Now they keep turing on and off at a more rapid pace only at night. I can hear a switch when the interior light turn on, it sound like it is below the glove box. This is only for the interior lights the exterior lights work fine. My twilight sentinal is set to off (where it has remained for years before this ever happened). What could be causing this, it's really annoying?