I had the exact same thing happen to me on 22 May 2018 on a 2-lane road. Stopped in traffic, engine stopped, but when I tried to drive a message said to shift to park to start engine. I did that, but the engine would neither start nor could I shut the car off, nor could I shift out of park to push the car off the road. After several frantic calls to the dealership (I had just had my oil changed and was driving my car home) and about 10 minutes, the car started working again. Naturally, I immediately drove the vehicle back to the dealership for diagnosis. Over the course of a day, they were unable to determine what had happened and why. Their response? "Seems like a glitch. Hopefully it won't happen again. If it does, have it towed back in."