I have an almost 4 month old male GSD, he bites and nips like all puppies do.. My problem is when we go for walks (not every walk, but most) he starts growling and then he lunges at my feet, ankles, legs whatever he can bite and bites hard while doing it and doesn't stop, it's like he's possessed! I have come back home bleeding every time trying to stop him.. I have know idea what's causing him to do this! Anyone have any ideas why this happens? Thanks in advance.