1999 Chevy Tracker Vehicle is hesitating.

For the past couple of weeks I have been experiencing some hesitation with my 1999 Chevrolet Tracker when trying to accelerate after stopping for a red light or at a stop sign. Just prior to this my vehicle quit on me when trying to back out of my driveway. I had the spark plugs changed and a new fuel filter put on and it has not quit again, but now there is occasional hesitation and a sputtering sound. The other day I had the a/c running and when I came to a stop sign it more than hesitated, it felt like it was about to quit. So I punched the gas and it kept going. I came to another stop sign about 30 feet away and it did it again. I turned the a/c off and when I stopped at a red light about another 30 feet away it didn't hesitate at all when the light changed and I accelerated. I havn't run the a/c since then, but still experience occasional hesitation. When I'm driving it rides well and doesn't have any problems except for making an occasional sputtering sound that comes and goes. Any suggestions on how to fix this problem would be greatly appreciated.