Just bought a used 2002 SE everything seems fine with it but noticed a beeping while sitting at a light? It wasn't loud enough to hear over engine noise while driving but sitting with the car running with the radio off it was noticable. I hadn't noticed it before and the next time in the car it was gone? Anyone have an idea what is might be? I may just be alittle paranoid from buying a used car but if someone could explain it I'd feel alot better.