Sounded like a small plastic bit tapping on a plastic surface!

I have it with or without a passenger on board. I also know and always remember to put the seat belft buckle back on the click. That's why it bothers me.....if I have a passenger, the seat belt is fastened, so where is this plastic clicking coming from???

 

I have the same problem on the drivers side... clicking goes away when i hit a bump, but whne i roll down the window and roll it back up, it clicks again. Weird, but not really that big a deal.