I have a gorgeous elderly male labrador, a wee bit hefty, and getting more arthritic with age.
He just had a weird 'funny turn' and I have no idea what the hell just happened!
He was lying quietly in the living room, when his head just popped up, started shaking from side to side, and his eyes were juddering about. As it continued his head started turning to the right somewhat but still shaking. It lasted for about 30 seconds, then he came 'out' of it, jumped to his feet and was full of beans 
He's now lying in the garden casting a beady eye on the NDN's cat, but doesn't appear sleepy or out of it at all.