Durango Transmission troubles

I have a 99 Dodge Durango, 117,000 miles 5.2L V8. When driving at low speeds the transmission "sticks" when shifting from first to second gear. It feels like the transmission is taking a little longer than usual before shifting into the next gear. At speeds over 35 mph, it shifts fine. The problem is off and on. Sometimes the transmission will stick, and other times it drives fine. When it does stick, sometimes the sticking is minor and sometimes a little more noticeable. It is annoying in stop and go traffic. It has been doing it for awhile now. I had the trans fluid and filter changed back in Jan. 07. It got a little better, but now it is starting back again.