Happened to me too! (But I am pretty sure my car did not suddenly go to neutral. My car stalled.)
My 2015 MB B EV suddenly stalled when I was waiting at a red light yesterday. The car has 300 miles on the odometer. I only had the car for 4 days, of a 3 year lease.
Here is what happened ...
On a busy street, the car was in "D", I stopped at a red light, my foot was on the brake, both hands on the steering wheel, definitely not touching anything else, A/C was on, battery's SOC over 90%, car suddenly stalls, all lights on instrument cluster came on, and it showed it was in "D auto", but GREEN READY LIGHT was not on, could not drive car. A/C is still on. There were no error messages.
(I know I was driving in "D". I also know it was in "D auto" at some point when all the lights came on in the instrument cluster. I'm pretty certain it was not in "N" at first when it suddenly stalled. When I saw everything in the instrument cluster light up, I might have put it in "D auto" from "D" when I tried to move the car? Nonetheless, no green READY light when everything was lit up in the instrument cluster.)
Foot still on brake, I put it in "P", I turn A/C off. I push ignition button to turn car off. I waited 2 seconds, I pushed ignition button again and turned car on. Back to normal, I put it in "D auto" and was able to drive the car again as the traffic light turned green.
I continued to use the car the rest of the day putting on about 100 miles without further abnormal incidents.
I will bring the car in to Mercedes service ASAP to see if there are any error codes logged. As mentioned, I did not see any error messages.
Very unsettling experience. I was lucky the car was not moving at the time, or going at high speeds on the highway.
I will definitely not let my wife drive this car until this problem is completely resolved.
I will let my MB service manager know this is completely unacceptable & dangerous.
Will keep everyone posted.
Here is list of owners who experienced sudden lost of drive or power:
http://www.mybclasselectricdrive.com/forum/viewtopic.php?f=8&t=380