Don't know if this applies to the 300Es, but I had a 1984 190E that did the same "stalling-at-intersections" routine. I had a complete service done, but when driving home from the shop it stalled at the first light. I stopped at the MBZ dealer a few miles down the road and had a tech do a test drive with me. He knew exactly what it was -- a faulty Fuel Pump Relay. Seems the originals were not hermetically sealed and contacts got corroded from moisture seepage. Popped the new (and improved) relay in and I was on my way (tho' $125.00 poorer). But, that money was well worth it to not being embarassed with my 190E AMG stalling in traffic.
Hope this helps!