Coach model and year will help folks answer easier. On our 17 Discovery we actually had a bad radio doing what you described as we drove down the road. Riverpark in Indiana was very helpful in working out exchange.  800 442-7717

Is this happening while driving, or parked, or both? I would suspect the ground if this occurs while while driving, I would look hard at the toggle switch that allows the radio to play when parked. As I previously mentioned after checking ours I couldn't find anything and called the radio supplier who did a warranty replacement and our problem went away.