I've personally have never heard of this problem on the 6.0 Diesel. Though this was a problem in older fords/chevys.

What happens is the starter gets too hot from being close to the exhaust. On occasion it can get so hot it will not turn over and there for once it cools down for 30 monutes it will start up fine.

So drive the truck hard on your way to the dealer to get that starter heated up. Then pull in shut it down, get a tech, and see if it starts, if it doesnt its that darn starter. If it does start your looking at a sensor or loose connections.

Hope this helps.