I can't say that yours is the same problem as mine was, but here were the characteristics of my problem so you can see if your symptoms are the same. It would occur reliably if both 1) my iPhone 5 was connected via BT and 2) I was listening to music from the USB drive. When those were both true, then any screen other than the Gracenote USB screen would be replaced every several seconds by that USB screen. When either of those conditions were not true, then it never happened. When it happened, I would first see the BT icon disappear, then reappear and that's when it would change screens. This happened all the time. The problem was resolved for me with the PIO880 GM Nav/Radio service update and I haven't seen it since.
(While we know it happens with iPhones, that doesn't mean it only happens with iPhones. While GM was trying to pin it on Apple for a while, I have to assume it was a GM issue since their update fixed it.)