Staying out of the debate, but my 1200g male spider doesn't do anything like that at any time, even feeding. It appears that he goes exactly the way his brain tells him to, however he's not perfect. His head does vibrate at random times, not all the time and not always at feeding. I always thought this was what was being refered to as the spider wobble. I guess it's just different degrees in different snakes, as was stated earlier.