Simple answer- Car Washing/Drying. If you take your car to a car wash and pay someone to wash, your going to get swirls.
The color of your car also will greatly enhance your swirls to the naked eye. Example, I have a white BMW X5, it looks good pretty much all the time (dirty or not). The white does not show swirls to bad. Now, take my Jet Black 135i....if you fart near my car the paint will swirl
I recommend washing the car yourself using a sheepskin wash mit, a bucket with a dirt guard, and use a waffle weave micro fiber drying towel and blot the paint to dry.
Next, anytime you polish or wax, use microfiber cloths only....