Kuhio did that all her 17 years. Usually near the food bowl.
She would put her back to the refrigerator and do the shakey tail thing like she was trying to spray and mark her territory. But nothing ever came out.

I don't think I ever remembered to ask the vet about it. If I did, I don't remember him being concerned. I think it's just one of those adorable Kitty Kwerks.