I have a Jack Russell Terrier/Chihuahua/Corgi mix that is extremely hyper active. Whenever I do or say something that he likes and that gets him excited, he begins turning in circles (even while he's walking). Why does he do this?
There are some medical issues that dogs get that can cause them to run in circles all the time, so you should consider taking him to the vet to have those ruled out.
Obviously, though, that's somewhat common behavior for dogs, especially breeds like JRTs.
Try exercising him a lot more for a few days, until he's entirely wiped, and see if that gets him to stop.