Initial daily startup problem
 

When my 1897 190E Benz is started each morning it runs very roughly and frequently stalls out when the transmission is put into reverse or drive. Strangely, if I wait about 30 minutes and try it again the car runs fine. The only thing I can add is when I unscrew the gas cap there is a significant sucking sound (is there a venting issue?). Things I suspect are condensation in the fuel delivery system or perhaps a cold start sensor.

Anyone have any ideas?

Probably a plugged tank vent, and hence low starting fuel pressure. I don't remember if the cap is the vacuum release (will have a hole it it if it is) or if the vacuum release is in the charcoal purge system, but I'm sure it is plugged. Try loosening the cap before you start and see what happens, or better yet, leave it loose and drive a bit, then let is sit overnight and try. If the problem goes away, you need to get the vent fixed. Pressure in the tank will do the same thing, causing excessive fuel pressure due to restriction in the return line.

You may also have a leaking cold start valve or warm-up regulator. Get those checked if venting the tank doesn't help.

Peter