1995 Geo Prizm

It's always ran really good for me. Until a few days ago, Everytime I come to a stop light it seems to want to turn off (but it never does) I would like to fix it so I won't be paranoid, like you can feel the car jump a little bit. It has done it in the past, but not as much as it has been lately, Im thinking it's the Timing belt, Or maybe the motor mounts, just need this fixed, probably something very simple.