2002 Hyundai Elantra 2.0 starting issues in warm weather

I have a 2002 Hyundai Elantra 2.0. In the cold, my car starts fine usually with the engine turning over once before firing. In the warmer weather, I have to crank it usually 4 or 5 times before the car starts. Sometimes it doesn't start and just sputters.On those instances I try it again and usually the same result. It wants to start but just sputters and almost seems to flood out. I sit for about 30 seconds and crank it again and it starts right away. I've been paying close attention to the sound the fuel pump makes when I turn the key to the "on" position but don't crank it and on the first attempt, I hear a high pitch humm and then a low pitch. I shut the key off and then to on again and a low pitch hum all the way through it cycling. It seems like a fuel supply issue but I'm not sure. I am going to replace the plugs and wires first but once the car runs it idles fine and runs fine on any road or highway no matter what the speed which makes me think its not the fuel pump. Almost like the fuel is draining back to the tank and when the pump cycles at first it is dry of fuel and then starts pumping when it hits the low hum. I have had a check engine light for a while due to an O2 sensor but have never had starting issues due to tthat. Could it be the pump? or soemthing else? Let me know what you think.