My 2015 ML350 just shut off while I was driving on freeway - 35- 45 MPH. The engine indicator on the dashboard came on and I didn’t lose any power. I tried to re-start, it would start but only to die back.
I have roughly 50-60K miles on it.
Then you need tomtow it to a service facility that can diagnose the problem. It cannot be diagnosed over the internet.