I have a 2004 Chevy Suburban Z71 with the BOSE in-dash 6-disc CD changer.  Occasionally, when I start the truck, the sound system is muted and has no sound.  The radio display is on and you can see which station is playing, can change discs, etc...but there is absolutely no sound.  This means no sound from the stereo, no chimes when door is open, no Onstar phone sound, etc.  It seems as if the amp is not clicked on.  If I let the truck sit overnight, sometimes all works fine.  Sometimes if I turn the truck off for a few minutes, it works too.  Sometimes, it doesn't.  I've never lost or gained the sound while driving....its either working or not working at START UP.  Is there a relay somewhere that I need to look at?  Someone told me this means that the amp is defective (ie it's ignoring the signal to turn on from the radio head unit) and it needs to be replaced.  However, if the amp was bad, wouldn't it just stay off permanently?  GMpartsdirect.com lists the amp at over $300.  I'd hate to go through the cost and work (I think it's buried under the center console) to replace it if it is something else.

Any ideas or quick fixes?

Thanks!