will not start

What is your question?

when my problem started I had turned off my car and it would not start like it was out of gas. the next day it started up and ran fine,untill i turned it off, then it would run for just seconds and die out. I let it set for a few month and had to replace the battery I figure I had reset the computer because it ran supper for about 2 months it was running after sitting over night until i turned it off, then it would just start for seconds it want. now it has gotten to the point where it only starts and runs for 10 to 15 seconds