I've had my 2012 Cooper Hardtop (non-S) for almost eighteen months. In that time, the following has happened three or four times, sometimes when listening to music from a USB stick and at least once while listening to the radio.

The music controls on the steering wheel will become ineffective--they won't do anything. I don't recall having tried the controls on the head unit itself. After about 5 seconds of this, the stereo shuts off completely, as if I had hit the power button. I can then power it back on again, and it will act normally.

The car has the regular stock non-HK stereo, with no aftermarket parts installed. It does have the Bluetooth option, but no Nav.

Any ideas? I'll be talking to the dealer about it, but since the problem is so intermittent I doubt they'll be able to do anything.