My old truck's radio would only play static for a whole year. The day I ordered a new one online, it came on clear as anything. I get what stella111 is saying about things messing with you, but I'm pretty sure it's just bad connections getting jostled. Vibration from slamming a door or even the weather changing can make a loose wire touch again for a while. It feels like magic, but it's usually just a crappy connection fixing itself by accident.