Car takes a few times trying before it sta...

since i bought my car from 2002 Nissan Sentra SE-R in 04' it takes a few seconds before my car will start as if the engine does not want to start. it takes 2 and sometimes even 3 times before my engine will start but i've change my spark plugs [expensive ones], checked my alternator and had my water pump replaced [yes i know...that's what nissan claimed was the problem when i took it back to them]. i have changed out my battery earlier this year. not sure what is causing my problem.