First two things that come to mind is a bad ground or a failing multi switch thats the stock that controls the lights function. First thing I would do is kill the lights and see if it still does it. Then push on the fuse make sure its still seated all the way down. Give the grounds a quick look make sure there clean and tight. You can follow th ground wire out of all the fuse panels and see where they go. Just out of curiosity how old is your battery by the way?