Transmission Not Engage problems of the 2004 BMW 330

I own a 2004 BMW 330ci. Driving in reverse out of my garage and driveway first thing in the morning, then shifting to drive when I reach the street, the transmission does not engage until about 3-10 seconds. The car will roll freely during this time as if it were in neutral. I have not had an incident or crash, but fear it is a possibility if this were to occur on a hill or if a car were to approach and I couldn't get out of the way. I contacted my dealership concerning this and they have never heard of it, despite numerous reports I have read online from other owners with the same problem.