Don't know if you ever figured out your issue, but I figured I'd throw my 2 cents in. Your car could possibly be going into "limp home mode". After several mechanics telling me I needed to get my tranny rebuilt at a price of about $1500, I finally found out from a tranny place that it wasn't my tranny, it was simply a sensor even though my check engine light was not on. My car was jerking because our dumb vehicles are made to do so if you have a sensor going to FORCE you to change the sensor. This is called "limp home mode". The repair that solved my problem ended up being a $26 neutral safety switch that is simple to install. Imagine how mad I was after 2 months of jerking and 3+ shops telling me it was my tranny.
Hope this helps.