Starting problem 91 300GE

[luky]

Hi guys, I have a strange problem with my 1991 300GE (3.0 litre 12 valve M103 with cat convertor, same as W124 300E or W126 300SE) 180.000 kms. When the car is not fully warmed up and I try to restart it shortly after shuting the engine down (e.g. after taking fuel), it won`t start again, the engine just turns but does not fire. If I wait about 5 minutes it starts without problems, if I help the car with the gas pedal I am able to start it after about 3 minutes. I have also noticed the very first morning cold start is quite difficult in colder weather, it sometimes takes 2 or 3 tries.

Any idea? Thx in advance.