BMW Repair: 323i Wont go into Reverse intermittently, thankyou, tranny

Question
My 2000 323i will not go into reverse sometimes. I've noticed when the weather is cold (I live in Florida, so cold is below 60F) my reverse will not work.  I can drive the car and it will work after the car is warmed up.  I don't see this problem during warm days. Could this just be a need for a fluid change, or require a more drastic transmission change.  Thankyou.

Answer
Is reverse the only gear that it hesitates in?Does first also hesitate?A fluid change will help if it can be done.Some of the newer BMW's have a so called life long fluid and unable to service normally.If it6 can be changed I would start there as you'll be able to see in the tranny for any debris.