B.M.A.C.

Hi my Jeep started acting up when its cold (after sitting), you engage drive and it will drive normally and then suddenly rev like its in neutral and then just as suddenly engage and drive normally. After it is warm the problem goes away. Even if you shut it down, as long as its warm the problem goes away. Any thoughts? I was going to change the fluid and filter check the bands, but not sure what else I should look for before I refill it Thanks