Why does my dog spin around in circles before he lays down?
While behaviorists are not certain about the exact reasons, dogs usually spin for the following reasons:
1. Survey their surroundings: Before dogs were domesticated, they would need to keep an eye out for predators before sleeping. Spinning around allows them to quickly see and smell their surroundings before rest.
2. Make a den: In order to make their sleeping spots more comfortable, dogs would have needed to clear tall grass, brambles and rocks. Spinning around would allow the dog to pat down and brush aside any obstacles.

Notice that these reasons are no longer relevant to modern dogs, who usually sleep comfortably inside safe houses. However, the instinct to spin around was trained over millions of years and so continues to affect their behavior