my car would not start up again, why?

i would get in my car( 99 infiniti I30). warm it up, and proceed to my destination. after finishing up what I have to do. I would get back in my car. But it won't start. I would wait around 5 to 10 minutes, then it would start. It does this every time, for the last week. what is the problem?

Quoc Redding
December 2009