2000 Chrysler Town and Country Transmission stall

Mornings in Central FL lately have been very cool 35-51 degree F. Almost every morning when I start the car and put it into Drive, nothing happens. No reaction until the car warms up sufficiently. If I press on the accelerator several times, it suddenly kicks into gear but until the engine is completely warm, it seems to sometimes go out of gear and doesn't respond to the accelerator. Once it gets going, there doesn't seem to be any problem. If I park and let it sit for an hour or two and get back in, there is no problem. Is this the result of the car being cold and the engine needing to circulate its fluids into the transmission? Or does it need transmission fluid? Or is there some other transmission problem that I'm missing? Should I be worried? In warmer weather, it never seemed to do this. It's been a problem only during the past few winter months. Thanks. Bruce