When the engine hasn't warmed up for 15 to 20 minutes, the automatic transmission won't shift into reverse or drive. (Like it is in neutral) This only happens after the car has sat overnight and has not warmed up first. Once I put it into drive and begin driving out of my parking space, it sometimes acts like it is in neutral. I have to sit awhile and wait for it to warm up before I can drive. When I drive it throughout the day, it is fine. What are the possible problems?