2006 F-150 won't start sometimes

Asking this question for the in-laws. They've got a 2006 F-150, and the other day they were driving it on the freeway for 30 minutes before stopping at a gas station. When they came back out to the truck, it wouldn't start back up. After about 10 minutes of waiting, it started right back up. Since then (that was a few days ago), it's done the same thing about three times, just won't start. The engine doesn't turn at all or anything. But he's told me that he went to go hook up jumper cables to give it a jump and then it will start up, before he even hooks the cables up to another car. He just hooks them to the posts on the battery, then it will start back up. And it's done that three times.

I have no idea what it could be. Curious if you all have any ideas.

CHeck connections at battery.

"He just hooks them to the posts on the battery, then it will start back up. And it's done that three times"

IOW, when the battery connections are 'handled' he gets enough current to start.

CHeck connections at battery.

"He just hooks them to the posts on the battery, then it will start back up. And it's done that three times"

IOW, when the battery connections are 'handled' he gets enough current to start.
Yes, I suspected as much, so I unhooked the terminals, which by the way were spanking clean, no corrosion, cleaned them off, and reconnected the terminals nice and tight. Problem now is that the problem was not consistent in the first place, so we can't really replicate the problem. Sure it started up fine after doing that, but we tested before doing that and it was starting up just fine at the time anyway. I haven't talked to him since I made the last post, so maybe that did it. I'll talk to him tonight and see what's happened.