I wouldn't worry until it actually doesn't start, since there are so many things that would make it hesitate you'd waste too much time worrying about them.
If you're feeling way pro-active though, have someone look at the starter, the fuel pump, the fuel filter, or the O2 sensor. Those a re a couple things associated with your problem.
But again, it's gonna be hard to tell which it is, if any, especially if your car has more than 50k (arbitrary number for the most part) miles. All those parts are gonna show some wear.