What kind of things cause a starter to work sporadically? Mine is off and on and autozone says my battery and starter both have signal

Could be a voltage drop on the solenoid wire. Toyota starters don't like it when they don't get 12 volts or more. If your not getting a solid 12 volts when trying to crank than you need to start looking for source of voltage between the solenoid to the ignition switch. Common cause is aftermarket alarms.

When the starter will not crank the engine, do you hear a 'click' each time key ir rotated to the start position? .. Then it will finally go ahead and crank the engine over so it will start??