transfer case grinding.

just wondering if anyone else has this problem.. or if it should really be a cause for concern.

i have a 00 Crewcab auto frontier v6 SE all that good stuff. anyway everyonce in a while if i go to shift into 4wd H it will grind and wont let me shift. and i have to turn the truck off and then back on and then it goes in just fine. or something if ive been in 4 for a while i cnat shift back into 2 becuase it does that same thing. but iturn the truck off and back on and its fine. and it doesnt do it every time, its random and not very often. and its not just those 2 combos, it will do it from N to 4L or 4L to 4H whatever, it has done it anyway u can think of.

anyone else have had or heard of this problem? and i never worried about it, it doesnt do it that often. but should it be something i have checked out? or any ideas what causes it?

thanks guys