That's a great looking Yoda!
I actually studied for a quarter under a guy who animated some Yoda in the Episodes 2 and 3, although he only mentioned it in passing. Charles Alleneck. Look for his name in ILM movies.
I like the fact that you avoided a lot of arbitrary arm waving. That would have been very un-yoda like.
Dhar has identified the big issue, sometimes called "isolated movement". In real life it's just about impossible to move one part of the body and not affect the ones connected to it (and the ones connected to those, and the ones connected to those...)
just moving a hand or head will cause the spine to slightly shift, to maintain balance and/or in reaction to the force of moving that body part.
I'd also suggest staging this from a 3/4 view rather than head on. As if he's talking to someone off to the side of the frame. It will be easier to do small hand gestures and small spine movements and make them look good.