2008 Kia Spectra

My car didn't start one day, seemed like dead battery got
a jump and it was fine didn't turn off. Next day it was
lagging to start like battery was low then other times it
starts up like nothing. Then after a few days it got worse.
It would try and turn on but it wasn't and I have to turn
and hold the key so I can start. I checked the motor oil
and it's fine. Check the radiator, it's fine I haven't checked
the transmission oil didn't think it would be the problem,
so I'll check it when I get off of work. Some times when I
turn and hold the key it takes awhile to turn on but other
times it turns on and when I let the key go it would turn
off. So I started now pressing the gas pedal and it stays
on and the car runs good. Then there's time when I turn
the key it starts up no problem and I don't hold the key
and don't press the gas pedal. Then other time when the
car is idling, it'll be rough but doesn't do it all the time.
The car only has 76,456 miles it's still a great car. I hope
y'all can help me out.