I assume the check engine light is not on - otherwise you would read the codes. I would begin with ignition - are plugs, wires, distributor cap and rotor all up to standard?

Beyond that, is the car hard to start at all (needing several tries or long cranking)? And when first started cold, is the idle ok for the first minute or so?

Another area to investigate is dirty throttle body and/or idle air valve.

Does your tranny shift properly?

You may have a vacuum leak or any of several other problems - but I would expect then the check engine light would go on, if it is bad enough for you to notice.