jeep intermittent power steering?

[mike b]

I have a 1995 jeep cherokee.Problem with power steering.ocassionally when i start it there is no power steering but when i shut it off and start it again is works.after idling for a while it quits working again then i shut it off and start it again and it is restored.anyone heard of this before. pump sounds find and it steers really smooth when it works