My 98 sunfire has a push starter switch that was just replaced sometimes it starts sometimes it doesn't battery starter and alternator just replaced it's tempermental what is going on?

Check all the connections. Sometimes the ends of the battery cable are corroded where they connect to the starter and engine. Switch itself could be bad. Try the starter either by shorting across the terminal on the solenoid or run a jumper wire to the solenoid and try starting it several times in a row. If it works that means the starter is probably alright and it is in the wiring somewhere. Try the same thing with the switch. Short across the wires at the switch and if the starter seems to work each time, it may well be the switch. The contacts in the switch may be getting burned and not making good contact.