Cockatrice6420
Songster
You probably have seen this before in other mammals & birds, then, and in humans, it is called titubation, or involuntary movements due to nerve pressure or damage.
Damage can come from disease, accident or genetics
The nerves can be a simple one in the neck, or full body ataxia.
You probably already know that sometimes it is an easy surgery to correct involuntary movement, sometimes in the case of disease such as MS and progressive Parkinson's, no cure can be made but there is some drugs that can bring some relief.
They're actually working on MS possibly being able to cure some cancers!