Olds alero won't turnover

I have been having on and off again problems with this car. Sometimes I have to get a jump and then the car runs fine. Now the car acts like it wants to turnover but can’t ignite. Changed the spark plugs ran fine for 2 days and now it’s doing the same thing. when the car sits for a while eventually it will turn over. Or when the car does turn on it sputters then dies acting like it’s not getting enough fuel. Could it be the throttle body, fuel pump, ignition system? I called an Auto parts store and asked about the OBD II test but i was told that only works when the service engine light stays on. I’m lost any idea’s?