Check your Tranny fluid level. If low you need to find your leak. If not low I would gamble on a fluid and filter change. A plugged filter would do this. You may also check your modulator valve if you have one (most do)
the diaphram can rupture and the engine will burn your tranny fluid. Also the modulator valve can cause all kinds of weird shifting problems. Modulators are cheap and easy. Under $20 at most parts stores and usually one bolt to hold it in. Good Luck.