99 Ford f150 4x4 won't engage sometimes?

I have a 99 Ford f150 with the 4x4 not engaging when I drive it a while. Seems when it's not been drove it's will work perfect if I put it in to low then into high. Any suggestions?

Any suggestions…

buy a Chevy.

Might be transmission wind-up. Drive a short distance in reverse or on a loose-surface road. That usually unlocks it.

Mine does the same thing, but usually if I put it in reverse and back up like 2 feet then put it into drive again it'll click in