Swirl marks are fine scratches that run in circles and show as a spider-web pattern in sunlight. They come from contact with the paint, not from the sun.
This page covers the causes of swirl marks, why brushes and cheap towels create them, and how correction removes them.
Every contact with the paint can leave a fine scratch: a brush wash, a dry wipe with a dusty cloth, a towel that picked up grit. In a dusty valley the risk is higher because there is more grit on the car to begin with.
Machine polishing. Single-stage work improves gloss and removes light swirls; two-stage removes more and finishes finer. A wax hides swirls for a few weeks and then they return.
No. Wax fills them temporarily and the pattern returns as it wears. Only machine polishing removes them.
Repeated brush washes are one of the main sources of swirl marks. A hand wash with clean media reduces the risk.