1994 Nissan Altima tranny or electrical

my nissan will be fine to drive for about 10 minutes, then it will lose all the gears. I can move the gear shifter and it won't go into anything, and will just sit there and rev up. If i shut the car off, it will go again when it restarts, but only for a little distance and then will do the same thing again. It seems like the warmer the car, the less distance it will travel. but whenever it is shut off, it will always go again. I have had the tranny filter cleaned and changed the fluid twice aready. Any idea what this is before i go to the garage???