My car (92 600SEL) has a similar problem. It always starts fine. If I did not let it to warm up to about 60C and shut it down, as if move it out of the garage on the driveway, next time it would not start and would flood as you describe. I had happened in any weather, hot or cold. The way to start it is to remove fuel pump fuse and crank until it starts, then reinsert the fuse. Everything I can think of was checked - sparks, fuel pressure, harness replaced. One last thing I suspect is extremely high oil pressure during start gets hydraulic tappets pumped-up causing partial loss of compression. That would require oil pressure test during start. For now I've learned to live with this and avoid shutting down cold engine.
Mike