Could be. Might also be a wiring problem.
When it comes back on, does it just come back up into the normal player screen, as if the display just turned off for a few seconds, or does it show the empeg/RioCar splash screen that talks about loading databases and such that you see when you first turn it on?
If it's the former, then the player isn't getting quite enough power, so it turns off the display (which turns off your amp) until it gets what it considers to be enough power again.
If it's the latter, it could still be the same thing, but with an even more severe power shortage. But that's unlikely. It might be a hardware problem. But I'll bet that it's the other option, anyway.
You know, this is bound to be a FAQ, but I can't find it.
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Bitt Faulk