my 6 year old choco lab that i use for hunting will all of a sudden start walkin funny, like he has lost his balance and his eyes will start rolling around and he will sometimes fall to the ground,sometimes he is responsive and sometimes not. these attacks r starting to become more frequent. sometimes he snaps right out of it and other times he just sleeps the rest of the day. today it happened and i fed him some popcorn and he snapped right out. what could this be?