If the issue of a fuel problem is ruled out, I would look at ignition next.
Try replacing the distributor cap, rotor, plug wires and plugs. A crack in the cap, or a worn spark plug wire that has rubbed itself on something will cause the problems you mention.
Could possibly be a coil problem, but I would do the above maint items first, which probably need to be done anyway, if it hasn't been done in the last 40k miles or so.