Car died while moving

I have a 1988 560SL mercedes with 80,000 miles (pampered by my parents until 3 months ago). I was driving on a city street (~20 mph) when every light on the dashboard lit up and the car died. I tried to start it three times before it turned over. I drove it home (~5 blocks) with no problem. I took it to my mechanic and made 3 stops on the way, also with no incident. My mechanic is at a loss.

I just read this and was hoping for a great reply. Mine has done the same thing 3 times recently and I’m now scared to drive it.