Does your dog do this?
Does your dog chase his tail? Out of no where? Mine does, his name is Duggar and he was adopted from the Dutchess County SPCA in 2015. He's a beagle mix and just adores people. His favorite activity is just laying on a lap and getting his belly rubbed.
Sometimes, when he get's bored he'll just start chasing his tail. It's very funny especially when it's unexpected. This could go on for up to 10 minutes if he doesn't get distracted by anything else. This isn't a regular occurrence so it's just a dog playing. If this occurs often with your own dog it could be a sign something is wrong.
Sometimes a dog will actually catch their tail as you can see in the video above and they can end up chewing on their own tail creating fur loss and skin damage. Dogs don't always understand when they are harming themselves especially when it's an obsessive behavior. Always remember to walk your dog daily which can help with general behavior issues.