I have an '07 Siverado Classic Ext Cab with the stock AM/FM/CD and door speakers. About a week ago, I noticed when I started the truck that the front passenger door speaker wasn't working. I banged around on the door panel a bit to see if maybe there was a loose connection, but nothing. Then about 10 minutes later, it just came on. No cracking or static or anything...sounded perfectly normal. This scenario is taking place about everyday now. Any ideas?