This is pretty good, but one of there must be a frame where the head is out of place because it looks like it's bobbling a bit.

I think the real problem is that there are too few  contact/passing freames. They're hardly noticeable and add to the 'spasming' effect.

I do like the pretty smooth look and bounciness.
 

I like this animation style!

To me the legs just look like they are spasming in place. There is not enough difference between the front and back legs. Same with the arms.

Excellent first animation! I really like the motion of the arms.  Super fluid.
Something seems off about the mechanics leg motion though.  I think it may be that the legs seem to swing forward straightened instead of leading with the knee.