Si2See

Hey thanks for looking to help. I know very little about chevys and my dad has a 2000 impala. It is such a great car and I love as probably as much as he does. Anyway when the a/c is on especially and he comes to a complete stop, when he starts off again it kind of lags like in the tranny sometimes even start to jump/vibrate. Not grining but it is weird it is just like a lag. Also it is leaking tranny fluid or burning it but would an auto burn it? We went to williamsburg 2 weeks ago and just in that trip it was missing like a half court or more of tranny fluid when we got back. However there are no smells, no leaks in the driveway no leaks to be seen anywhere. What could be the problem?