engine wont start without help

after the car(2003) is warmed up,the car wont start unless I step on the first,then it runs fine.what could it be?

Either bad injectors or a bad fuel pressure regulator. This usually accounts for engines that won't start when hot. I would check the fuel pressure to see if everything is alright in that respect. Once you shut the car off hot wait about 15 minutes and then check the pressure at the rail without starting the car or turning the key to the on position. If the pressure is low then the problem is the regulator. Bad injectors can stick open and allow the pressure to bleed off after the car is shut off causing the car to be hard to start. This is hard to identify but can be the cause of your problems. Also quite expensive to repair. There rar other reasons but these are quite common.