My front left drivers door speaker suddenly stopped working (produced no sound) while driving. However, in park with the drivers door open, it worked fine. I changed radio stations, ran the CD player and got same results. Three hours later it worked correctly with no investigation or tinkering on my part. Anyone been thru this?

 

Sounds to me like a loose connection. I'd start with checking the large black wire harness between the door and the car. Try to wiggle it with the music playing to see if it effects it. Push it firmly into the door.