Get Your Dog Care Questions Answered by Experts
hello and thank you for using this site to help you. Because he is sitting on the floor and going in a circle he may be trying to relieve his anal sacs. If he was groomed yesterday and this has started happening today then they may have tried to express the glands during grooming.
When dogs have a bowel movement this usually breaks the sacs open, but if the stool is not firm enough then the sacs don't break and they can become irritating to the dog.
I would take a peek and see if there is any swelling or sores on either side of the anus.
In the mean time I will direct you to a site on the anal glands for further reading and to know if this is something your vet needs to look at.
Anal sac abscess picture http://www.my-pet-medicine.com/wp-content/uploads/2006/10/180px-Anal_gland_abscess.JPG