This happen to me 3 times. I would recommend taking it to the dealer. I think it's very unsafe losing power. My 09 4.8 is still in the shop. Two weeks and counting as of today. They think it's a wiring harness, per BMW NA recommendations. They replaced the throttle harness and throttle body with no success. I hope to get an update today on vehicle. I'll post once I get the car back.

I have two young kids and I'm not willing to risk their safety. IMO.