tuned318 After storing my car for just 2 months it really didn't want to start again.. I cranked it forever untill it started.. then It was only running on 3 cylinders untill it warmed up. I also had a lot of white smoke coming from the tail pipe and a loud clicking noise that lasted 30 min. I hope it doesn't do this to me again next spring because i just rebuilt the motor over the winter.
Unless you blew the head gasket the last time you drove it, or something has siezed in the motor like a valve or somthine hydrolic. then i would just run the motor for a while and see what happens. I know it's not the best idea but as long as your getting a good spark from the ingnition coils, the plugs are good and the motor is turning fine then you shouldn't be able to hurt anything. Keep in mind you could have an air pocket in your oiling system or you might not be getting pressure to the hydrolic lifters and timing chain tensioner. Id have a mechanic drop by and test your oil pressure when you start it again. Without oil the M42's won't run properly.
any more questions just ask me.. i'm not a mechanic but i've spent a lot of quality time with my motor.
The major difference between my 318is and an e30 M3 is that the noises come from the engine and not the passengers