2003 starting issue

Hi, I have a 2003 Mustang GT and it has a hard to diagnose starting issue. About once every 15 - 20 starts, it just cranks. Doesn't matter how long you let it, it just won't start. But if you stop and re-turn the ignition, the very next crank will start right away. And then it will be fine or the next 20 starts or so. Obviously, since it's under warranty, FORD can't make the car do it when I've taken it in and it doesn't show any codes. I'm sure after the warranty expires, they'll miraculously diagnose the problem. I assume it has to be spark or fuel, but it's such a seldom occurrence, I'm not sure what could make it act that way. Has anyone had a similar problem or ideas. Thanks

A lot of those problems end up being a weird fuel pump, that only acts up now and then and can do so for the longest time before completely failing. Just dont get too mad at the dealer cause theres only so much they can do. If a tech cant get it to act up, they really cant do anything warranty wise.