Cast iron does not chip or crack the way glass does, but it rusts if moisture gets trapped and its seasoning scratches off against another pan. A light oil coating and a paper layer between pans handle both risks.
Pro tip: A well-seasoned skillet with a fresh oil coat can double as a rust-proof container for lighter items nested inside it during the move.
Watch out: Never pack a cast iron skillet even slightly damp or unoiled; trapped moisture in a sealed box is one of the fastest ways to start rust on bare cast iron.