Nav/DSP stereo volume dramatically changes on its own

[admranger]

Apologize in advance if this has been covered, but I couldn't find it with my search skillz.

So the volume is changing much more dramatically than just the speed adjusted volume would normally do it. And it can change while stopped at a light waiting for it to turn green...

The change is from normal listening levels to what seems like nearly max volume, then it drops back again. Does this when listening to the radio or through the intravee (iPod) system. However, the interesting twist is that when listening through the iPod, it'll switch back to radio when it plays loud then switch back to the iPod. It's a short deal, a few seconds each time, but it is super annoying when it plays so loudly.

I just got back in town so I haven't looked at it yet (and it's 100 in the garage), so I don't have any preliminary diagnosis.

Doesn't sound like the amp though with the switch of sources too...BM54 (or whatever it is?).

Thanks for any help!