What is the cause of a 2001 Buick LaSabre Custom not starting all the time?

What is your question?

I changed the fuel filter & my 2001 buick lasabre custom started fine for 3 weeks. Then after 3 or 4 tries it would start & start fine for another 2 weeks. When key is turned 3 or 4 times there is no sound & then it will start by either key.The problem started months before changing filter.The car always starts but one day it may not start at all.