1998 Buick Park Avenue INTERIOR ELECTRONICS

Interior problem
1998 Buick Park Avenue 6 cyl Front Wheel Drive

About 2 weeks ago, the car was left with the windows down, and it rained very hard into the car. When I returned to the car about 2-3 hours later, as soon as I started the car, the AC kept turning itself up and down, the radio changed the channels, and the windshield wipers turned on. Since then, all that has stopped and corrected itself, but since the interior lights randomly turn themselves on and off. When they come on, I can turn the switch on the dash for them on then back off, and they will go off, bot soon come back on. What could be causing this, and how can I fix it? Thanks.