I'm guessing it has more than 100k-120k miles on it?
when my mechanic hears 'jerky at a stop' with an AT, he blurts out (quite involuntarily it seems) torque converter. Which, since I'm sure you're curious, is not cheap (for a shop) or easy (for you or the shop) to fix.
If you have an AAMCO around, take it there. They do free diagnostics for transmission problems (although you may have to bring the
coupon from their website).