Is he getting enough to eat? If he's stalled, do you free feed hay or does he get turn out?
There's two things I can think of. He's wanting something to graze on that he's not getting, so he's turning to the shavings...or, he's still hungry. When Hoover came from the slaughter, he did the same thing (hence the name Hoover), because he was extremely underweight. It doesn't really hurt them, but my best guess is he's wanting something to munch on between meals.
"Sit tall in the saddle, hold your head up high. Keep your eyes fixed where the trail meets the sky. And live like you ain't afraid to die...don't be scared, jut enjoy the ride." - Chris LeDoux