Heidi, I would definately try and change the filter and fluid. After the tranny fluid heats up, particles move more freely in it and sometimes a filter that needs changing will give you signs. I'm not saying this is the problem but my Wife and I have only bought a new car once in our lifetime so all the other 100,000 miles+ cars we have driven got a tranny fluid and filter change except one with a 700r4 and it started giving us probs. Did the filter and fluid change and drove the car another 25,000 miles until the engine quit. Filter kits are really cheap and only take about 45min if you can adequately squeeze under the car. I'm starting to get a serious gut so the jackstands keep getting taller and taller. lol Good luck with it. Nothing worse than a sick baby, er I mean TA.
James