I have also had this exact thing happen in both B3 and B7

I had a similar thing happen last night -- only time it ever happened, and today it's working normally.

I shut off the car, the empeg went into standby, the CD player folded up its motorized face -- and then all by itself the empeg came back on and continued playing -- except that the amplifiers were off so not very much noise came out. Pressing and holding the top panel button put it back into standby, but 5 seconds after releasing it, the empeg came back on.

Pulled it out of the dash, put it back in, and after 5 seconds it booted up and started playing, again without amplifier. Did this twice more, same effect. Fiddled with ignition key, turned ignition on and off, no change in behavior. Finally just pulled it out of the dash and left it.

This morning, everything works fine.

Curiouser and Curiouser, as Mr. Dodgson would say...

tanstaafl.