i have a 97 318is. does the same thing when i haven't drivin it in a while and it's been in the cold. once it was about 10 degrees and the car had been sitting outside for a month, so the motor itself was probably 10 degrees. i started it and it was pretty violently idling, the exhaust was shakin all over the place, and wheni'd give it gas i'd see black smoke coming from teh exhaust. thats normal to expect with any car when you start it cold.