Misha is nearly 11 (August) and has been doing these little twitches for a split second every once in a while. It's like a very, very mild shudder and he doesn't appear to be in any pain and seems very mentally with it. His only problem at last vet visit (7ish months ago) was some arthritis which he takes rimadyl (1 or 2 doses every 2-3 months if he's flung himself about and sore). Other than that he's been really healthy and all tail wags. Any advice?