My cat turns his head to the side when he’s chewing the food with his grinding teeth in the back; perhaps the food is on one side of his mouth and he’s leaning toward it.
He’s also a complete snob. If the bowl isn’t full–not near empty, just not full–he bugs the crud out of me to fill it.
formerly known as LauraRae
I’m a Raggety Ann in a Barbie Doll world.
My cat (Mr. Bean) doesn’t do the head-shaking thing, but when he’s done eating, he’ll scratch the floor around the bowl as if he’s just used the litter box. Maybe he’s sending me a signal that he’s equating his Meow Mix with excrement. Finnicky, indeed!
Neil, Neil, orange peel!
My cats don’t shake their heads side to side either. One of them tends to dips his paws in his water dish after he is done and walks around in a little puddles he makes. I guess hes just cleaning his paws.
My dogs do this after they attack and kill the stuffed dog toy or the helpless prey rope. For the DOGS it IS a “got the prey… now I must break its neck so I can eat it” instinct.
BUT my cat has the SAME reaction yours does when eating… but its more of a “MAN this stuff is sour and hurts my jaw joints” action then a killer instinct. Maybe they just really have to choke the catfood down… 
My three kitties at my parents house do that, doug. They’ll get some food, then chew on one side, then move their head to the other, chew on that side, and over and over. They only do the vicious quick side-to-side movements when they’re attacking something.
When are you going to realize being normal isn’t necessarily a good thing?
My 2 male cats do this. One of the females just eats politely, but the other sticks her paw in the dish, pulls out a handful of crunchies, and eats them off the floor. My mother’s cat (offspring of the one who paws out the food) does the same, except she pulls out one peice at a time and puts it in her water dish, where she leaves it until the water gets changed.
my cats get dry food only & do all the above: shaking their heads, grinding on one side & then the other, lifting out & scattering food on the floor. one cat will stand in the water bowl while he drinks. normal inborn behaviors.
the gross one, tho, is backing up while they grow up. leaves a much lonnnnger trail to clean up. my sweeties . . .