I had some what of the same behavior about a month ago (she is 5 months old now). Huayra would do the same mouth snapping thing at me and sometimes would even tackle and try to dominate my legs (grabbing my leg and hugging it with her paws crossed off). Which is a big no no. Especially with a GSD. You do NOT want them to dominate you, EVER.
I am not a professional trainer at all, I've been to the beginner level and starting intermediate level training this weekend and I just learned to correct her behavior in junction with her trainer.
From what I can tell... Your pup is trying to dominate you. A couple of fixes...
During food time, like mentioned... About 30 seconds your pup gets into eating grab the bowl right under her mouth and hold it while staring at the dog. She/he might growl at you but it's ok. You keep doing that till she/he obeys/stops trying to be dominating.
Another thing I found extremely useful (which some might say its ridiculous) is to pin him/her to the ground by holding the fat behind their ear and on top of the neck. Hold her/him via that. This will NOT hurt the dog but will make him/her understand that you are the master.
Moms nip their children by their snout or pin them via that upper neck area to correct behavior. I wouldn't suggest the snout part as we have hands and not sharp k9 teeth. You could hold it shut though but not as effective as the neck trick.
From my experience the GSD is a very intelligent, high energy and stubborn as **** breed. It's ok though, it will pay off given the right training. Even at 5 months my GSD is great, she still is a puppy especially when going to places as in... Hyperactive and over exited... To give you an image... She tries to swim in concrete with all her paws... However that is fixed with the "gentle leader" leash piece.
I hope the 2 tips I gave helps as they made me and my girlfriends life a heck of a lot easier!
Sent from Petguide.com Free App