Why does my cat use the litter box every five minutes?

This doesn't always happen, but sometimes my cat goes in and out of the litter box four or five times within a half hour. He paws around, sits for a bit, paws some more, and then leaves. And then comes back to do it all over again. I go and check the box after he's done, and he hasn't left anything... show more This doesn't always happen, but sometimes my cat goes in and out of the litter box four or five times within a half hour. He paws around, sits for a bit, paws some more, and then leaves. And then comes back to do it all over again.
I go and check the box after he's done, and he hasn't left anything new. Is this a sign of a larger problem or does he just like playing in the sand?
8 answers 8