Rodders started to do this shortly after we started at puppy training classes and my neighbours thought it was hilarious to see me trying to entice him to walk a step or two. I tried treats, picking him up and carrying him a few paces and then trying again, gentle encouragement, firm encouragement, a little dragging, but I am not sure any of it worked. He just likes to sit and watch the world go by.
Now there is no stopping him once he is on the lead. But he does still like to stop and watch if he is somewhere new or there is something going on that he isn't sure about. I am happy to let him sit for a minute and then I use a brisk 'This way' command and he usually follows me.
Rodders the Mini Pup, born 10/08/11, came home on 09/10/11
Creggan the Mini Pup, born 17/03/13, came home on 01/06/13
Proud of my Scottish Heritage