Our pup (14 week old Bouvier Des Flandres) is doing this too, but oddly, only when I am walking around in the morning or night in my Boxer shorts i.e. legs exposed.
The big problem for us is that he is getting bigger and so the bites are getting higher up. It's always as I am walking away from him, and the nip comes from behind on my legs. This morning he reached my bum and it REALLY hurt!
Being male myself, I am slightly nervous of the fact he might start doing it from the front.
Night time toilet visits to the garden are the worst, as I get nipped all around the garden unless I throw some trousers on first.
He'll be able to go out in public for the first time on Sunday (waiting for the inoculation immunity to be ready) so I am hoping that he calms down after finally "mixing with other dogs" and getting tired out in the park!
Is this realistic, or should I find a friendly farmer who fancies a free herding dog once a week on a Sunday to satisfy my dogs desire to herd?