I had exactly this problem. About 3 months ago I purchased 4 fancy silkies from a breeder. I've raised 100s of silkies I've hatched on medicated but ran out, so these ones got regular Kalmbach's grower. One almost immediately started doing that same thing as a three-day-old chick. Plus, would all of a sudden zip off to the opposite side of the brooder and shake head some more. I thought vitamin deficiency, so gave Poultry Cell water one day, Hydro Hen the next, fresh water the next, then kept repeating this. Nothing helped. I ground up some sunflower hearts to mix in their mash, which are high in Selenium and Vitamin E. I did this for a week. No change. I called the breeder, she had no idea either. No matter what I tried, this chick never stopped doing this for two months.
Fast forward two months, I put them outside in a pen with a temp coop. I noticed within a couple of days, she was improving. I don't know if that was a coincidence. They've been outside free-ranging now for a couple of weeks, and I've never seen this behavior again. I've since hatched a few more batches of my own, nothing wrong. To this day, I have no idea what was wrong with her and assume she outgrew it. I hope if nothing else works for you either, at least yours will too.
