'93 Impreza 1.8 Engine: Starts fine for days at a time, then won't start. Usually if you try again later, it will start.

starter might be going out not sure? Next time it wont start try tapping on the starter if that get it to start than start looking for a new one.

Could be starter, ignition, or a wiring problem. I'd vote for taking it to a reputable shop and asking them.