I agree with Benzmac -- my first choice of culprit is the Fuel Pump Relay. Had the same problem you describe on my '84 190E. I thought a complete tune-up would clear the problem, but I stalled at the first stoplight on the way home from the shop. Stopped into the nearest MBZ dealer and a tech found the problem to be the Fuel Pump Relay. They'll run ya about $130.00, or so.