I've had the honor of fostering many a Cocker Spaniel for San Diego Spaniel Rescue during the 8 years that I was the Director. And boy did I learn a lot during that time! Early on in my foster days, a darling blind Cocker in my care, named Lacey, had symptoms suddenly crop up. What was going on? She could only walk in unsteady circles (in one direction only), her head tilted off to one side, and her eyes were quickly moving from side to side, back and forth over and over again. Off to the vet we went, and I heard for the first time (but not my last) "Vestibular Syndrome". It is often called "geriatric vestibular" or "old dog vestibular" since it is usually found in our older canine friends, but this isn't always the case, and those names are misleading. I learned that there are usually two types of Vestibular: one caused by a brain tumor and another caused by ear issues or with no known cause. Some people will say that stress or trauma can preceed an onset of the symptoms. My vet told me that if it was originating in the brain, we would see the rapid eye movements (called nystagmus) going up and down, and if it was idiopathic (without a known cause) or inner ear related, we would see the eyes moving side to side. For Lacey's symptoms, that alone helped calm me down! I also was told that her case wasn't as severe as it might be ... in some dogs the loss of equilibrium is so severe that they actually roll over and over, attempting to regain their balance.
If you Google "Canine Vestibular Syndrome" you will get a LOT of information - verify everything with your veterinarian tho! This blog post by Luisa Serrano is one that caught my eye, and includes videos so you can see what it looks like.