Hesitant start after short drive
 

I am begining to see a pattern develop, does anyone know the cause? My 1996 C280 (with 203K) is hesitant to start and then knocks for a mile or two if I have parked it after just moving the car a short distance like backing it out of the garage then letting it set in the driveway for a couple hours. I started the car, then moved it about 50 feet into the garage last night about 6PM. This morning at 8AM it took three tries to get it to start and then there was knocking and it smells like its running rich. I never have this problem if I drive it normally the 25 mile run to/from work. The spark plugs get changed every summer, the oil is changed every 4K, and I always run BP 93 Octane Gas. The garage stays about 45 - 50 degrees F on a cold night. There are no CE lights. Otherwise, the engine runs smooth. Any idea where to start looking?

Thanks,
Brad

A couple of wild-assed guesses on my part.
Pull the vacuumline off the fuelpressure regulator and see if there is any evidence of gasoline.
Next step would be to pay someone to check/monitor fuelpressure ( after shut-down, during start-up & running engine ).
Gotta start somewhere. ;)