Somewhat common in adolescent West German Shepherds.  Urination is often followed by a clear, thick mucus substance. This is caused by inflammation of the developing vaginal tract. While bacteria is often involved, it typically clears up without assistance or Meds.  However like basically every other simple ailment in dogs, this is one that the American veterinarian frequently scams dog owners with.  If your puppy should develop this ( don’t be following your puppy around, watching and micro-managing them) but if you do notice such for longer than a few weeks, then contact your Breeder ( if you have a real Breeder ). However Vaginitis typically resolves itself after a few weeks.