Why does my dog turn around 4 times before sitting down?

His Chakras are out of alignment. Take him to the closest yoga joint in your area. Giving your dog ayahuasca could also help.

This behaviour goes right back to dogs in the wild - they are making a nice flat area to lie down on. Nothing to do with poles or anything else!!

What Veschengro says about his sheepdogs is the reason dogs turn in circles before they lay down. It is a behavior that is not necessary but it is a behavior many dogs have. Has nothing to alignment of magnetic poles at all. Just to smooth out an area to lay down on. More common than you think.

My sheepdogs do exactly the same in the high grass, in their off duty times. They make their nest to sleep in by walking in circles in order to flatten out the vegetation usually on top of an elevated view point above the ewes and lambs..

On the hot dry nights I also do the same and sleep on a simple groundsheet.

Instead of in a bender tent or a shelter

he's making his place or temporary nest.

if he was outside he'd be patting down leaves or whatever

It has nothing to do with the poles or horoscopes