reverse

i don't know if this is common or what, but every once in a while after starting up my car and trying to shift into reverse it doesn't go into the gear all the way and if i'm not paying attention it'll grind the gear. so i pull the ebrake and put it in neutral. then i shift back into reverse and it works and off i go. sometimes it does this a few times before it goes into the gear fully. my friend said he had a problem like this with his 200sx. it doesn't seem like a big deal, but i'd like an explanation if there is one..

mine does it too and i just pump the clutch twice and it goes right in
i dont really mind it as long as the rest of the gears work.