A similar thing happened to me. Both headlights would come on in the middle of the night for no reason. The rear lights would still be off. The Dealer just uploaded the latest software build (Stuttgart release them several times a week) and the problem never happened again. BTW, the car is clever enough to cut power to anything that is on if the voltage drops to the minimum set for the starter motor to fire so this kind of fault won't leave you stranded.