1991 Mazda 626 My car stalls and then shuts off !

Engine Performance problem
1991 Mazda 626 4 cyl Four Wheel Drive Automatic

Now I don't know to much about cars, I know hardly anything at all but my 1991 Mazda 626 that I received from a friend was working perfect. I had just recently got the oil changed in the car and the brakes, transmission flud and brake fluid. Maybe a month after getting my car serviced I was driving around doing errands and my car started to jerk or stall a little bit after I would stop for a long period at a light or a stop sign. Now I went on the freeway after that it rode perfect and right when I got off the freeway, stopped to make a right hand turn the car jerked a little and then completley shut off! The next morning after having it towed back to my place I started it up again, it was wroking; it turned on fine and was driving fine. I took it out for a spin around the block to see if the problem was really gone, and once I got it out of the driveway and had to stop at a stop sign it started to jerk again. Another stop sign came up, and it jerked and then shut off again. When I have the car on in park and it's just sitting there the car is perfectly fine, but when I switch over to drive that's when it shuts off. I haven't gotten it serviced for the problem yet because I don't want to pay 80 bucks for someone to look at it and tell me that it's the battery, or that it just needs gas. So what's going on with my car? Is it the battery? Or does it just need a Tune up? Please help me ! :)