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.