The spider "wobble" is actually a pretty well-known thing, and my understanding is that all spiders do it to some degree. My female spider does a corkscrew movement with her head and neck sometimes. Before I bought her, the breeder I got her from told me that she didn't have any wobble, but I think maybe he just didn't notice it, because he kept her in a rack. Now she lives in a glass tank in my bedroom, so I see her come out and corkscrew her head sometimes in the evening, when she is most active. She only does it when she is in an upright position, looking toward the top of the tank. You can't tell at all when she slithers or feeds. Otherwise she seems completely normal, so I have decided not to make a big deal out of it.