Bucking of my car

I have a 2001 Hyundai accent, 101,000, 4 cyl.
I was driving home, it was raining and my car started bucking, it bucked when I would go from being at a stopped position to moving not as much when I stayed at a go pace and It would really buck if I went in reverse. My transmission fluid was pink and it was at the proper level, what could it be before I go to get it fixed and they try and nickel and dime me.