2001 Saturn L300 Car Problem

Transmission problem
2001 Saturn L300 Automatic 104000 miles

I have a 2001 Saturn L300 that I just bought, and it has been in the shop for almost a month. I have only driven it for 2 days. I was driving home one night when the reduced power light came on along with the Service Engine wrench light, and the Service Engine Soon light. When the lights come on the car begins to shake very badly and it slows down to about 20 MPH instantly. If I turn off the car and then turn it back on it will run okay again. The car shifts pretty hard. If I keep it going slow it dosn't do it as easily but once I start going faster it does. It has been in the shop 2 previous times and they have replaced the computer and a few other parts that I can't remember at the moment. I have no idea what could be the problem. I know there are recalls on this but I am not sure if this would be under any of the catagories of the recalls.
Any help would be greatly appreciated if they don't fix it this time.
Thanks