I would check your trans fluid level. You have to have the engine fully warmed up and then with the car jacked up AND running in drive or neutral(not park!)... remove the fill plug above the ATF pan. You add fluid until it starts to flow out. Then screw the fill plug back in. And you are done.
BMW says the trans is a lfietime fluid. The people who make the trans ZF say it needs to be changed every 80K kms.
You can find the proper fluid and filters here... I think this is the one you need. But check your trans number first!
http://www.thectsc.com/index.php?p=p...d=187&parent=7
Dack