Turn key to start engine will not always work,why? on 1991 Mazda Protege

Sometimes when I turn the key to start the engine, I have to keep turning the key until the engine starts; other times, engine will start during my first try with the key. What causes this?
This problem occurs either with the engine cold or hot, it does not matter. It does not sound like the starter.

Asked by for the 1991 Mazda Protege
starter maybe going bad, or problem with ignition switch, starter relay, corroded wiring, could be a few different things..