I don't know 190's, but many MB's have a crank sensor (electromagnetic sensor at the flywheel attached to a wire) which sends a signal to the car's control system. Our 124 had a similar problem, where the engine would just die, anywhere, anytime, very random, and start back up easily. It never died for long, sometimes only for a fraction of a second, sometimes for a couple. EXTREMELY nerve-racking on the highway!
It turned out the sensor had frayed insulation and a poor connection at the bellhousing. Replaced it (about $100) and the problem went away.

It is easy (on the 124 anyway) to replace, if you can locate it.
Good luck.

__________________
Peter
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K