My Cat's Worrying Behaviour

I have a female tortoise shell cat who is now 14 yrs old. Several times now I have noticed her head moving like she's nodding her head.
   
I'm worried because I used to work in a pet shop and when a Rabbit exhibited this behaviour it was never good news and we had to put them down.
   
Could it be an Ear or a Brain problem?

It's hard to tell. You should have a full exam done, and blood tests if the vet thinks it's a good idea.
   
Is there anything else odd about the cat, that's new?