Sometimes when I try to start the engine it sounds like spinning gears making a high pitched grinding noise, like the starter isn't engaging or something. After I try it a couple times it will start and seem fine til it happens again. Like I said it is random as far as I can tell and fairly intermittent.
1999 Ford Expedition random intermittent problem when starting on 1999 Ford Expedition
I would recommend to diagnose it, but it sounds like a starter problem. Make sure to check the flywheel teeth when you remove it.