[iananderson02]

Good suggestion but crank or cam position sensor will almost always throw a check engine light with the relevant code.

The strange thing about this is that the car runs really really well after a VERY short time, about 10-30 seconds. Not long enough to really get any substantial heat into anything. disconnected from the engine (such as plug wires) I don't think it is caused by condensation unless its inside the fuel lines that is...

I'm starting to think its a leaky fuel injector. Perhaps the cold is not the cause, it may just be a long period of non-running (which would allow the car to cool off), leaving time for the leaky fuel injector to drip until the pressure bleeds off. Spark plug gets wet with gas, car becomes flooded in one cyl and thus the rough running. As soon as the plug dries and cleans itself from the internal cyl temp it runs well again. I know that many e36 owners have experienced this after 10 years and 100k+ miles.