A quick spin makes everyone laugh. Then your dog does it again, and again, and you notice the fur at the end of the tail is wet from chewing. The same visible behavior can be occasional play, a response to irritation or pain, or part of a repetitive pattern that needs help.
If your dog bites the tail, injures the skin, seems distressed, or has started doing this suddenly, arrange a veterinary appointment. Your vet can check for injury, skin problems, discomfort around the rear, and other medical causes. If the behavior is intense and cannot be interrupted, don't wait for a wound before seeking advice.
Watch the pattern without encouraging it
Note what happens just before the chase. Is it after a long period alone, when visitors arrive, or at the end of a stressful walk? How long does it last, and can your dog switch to a familiar activity? A short video for the vet can help, provided recording does not delay care. Don't tease your dog into spinning for a laugh or scold them for it. Either response may add pressure or attention without addressing the reason.
Give your dog predictable walks, sniffing opportunities, rest, and activities they enjoy. If you see a mild, familiar build-up, invite them to a toy or scent game before they start circling. But enrichment is not a replacement for an exam when there is discomfort or self-injury. Your veterinarian may suggest a behavior specialist if medical causes are ruled out and the pattern persists.
The useful question is not whether a tail chase is "normal" in every dog. It is whether this dog can stop comfortably and go back to the rest of their day.
Sources: VCA Animal Hospitals: Why Dogs Chase Their Tails. VCA Animal Hospitals: Compulsive Disorders in Dogs.