My paddletails do that also. I think it is a warning thing. My paddletail that I have had for about two years rarely does it anymore, but the new one I got does it every time I come close. I think he's telling me to back up.
"Pachytritons are known for their chemical communication. Tail fanning at all times of the year is one distinctive trait exhibited by both sexes, and this behavior is not always associated with mating. Males will fan wildly when trying to get a female’s attention, and both genders will moderately fan when approached by others, or when disturbed."
this is from the caudata culture species section on paddletails.
sorry I don't know how to post links