That's normal behavior.  All of mine do that in one way or another.
Their movements are all different, but all of them move their heads to
reposition the food bits.
 
Their little mouths are made for ripping flesh off a carcass, not for
chewing kibble bits, so they sometimes have a little difficulty with it.
 
You might also try a different brand of food with a different shape.  Some
people claim the little cylinders like the Marshall's food are difficult
for them to chew.
 
Roger, Digger, Bear, Fox and Stripe
[Posted in FML issue 3687]