2007 Taurus shiifting rough between 1st and 2nd
 

I have a 2007 Taurus with 282,000 miles on it. It has been a great vehicle so far but recently it has started shifting rough between first and second gears. It doesn't do it all the time just every now and again. When it does it though it will shift rough maybe three or four times and then it shifts okay for a while and then starts back over again. Anyone have any ideas what it is, or is it just time for the transmission to go. Oh I checked the fluid and it was 2 quarts low. I added some to fill it up and have looked all up under it looking for a leak and can't find one anywhere.
Thanks Henry