Originally Posted by NJ Shepherdfan
I know i'm going to hear that he is not socialized enough and needs to get out and see more people. I'm going to hear that i shouldn't raise a gsd in a truck. I'll hear lots of negative things and i really dont want it or need it.
Not from me.
From your description it sounds like he really likes people and the flailing and nipping is purely out of control excitement, not aggressive behavior based on fear. What I would be doing is TONS of work on impulse control. Right now he's getting to meet people in spite of his inappropriate behavior, so he's being reinforced for doing exactly what you don't want him to do. To fix that you're going to have to make sure that this behavior NEVER works to get him what he wants, while training a new behavior for polite greetings. The most difficult part of this may be getting people to go along with it.
If when you're busy with your truck and can't really control people from approaching him, you might want to consider putting him back in the truck after he goes potty. And then when you have a few free minutes, bring him out and get some nearby people to work with you on it. Once he figures out that the ONLY way he gets to meet people is to sit calmly, and that if he breaks his sit and starts to flail about, they either stop and freeze (best if they ignore him and look away too), or even back further away from him, his behavior should start to improve. The second he gets excited and bitey, the people leave. His behavior controls his access to people.
We worked on an exercise in puppy class where all the dogs were tethered to the hooks in the walls, room, and the people in class went around the room and approached each dog in turn. If they could get close enough, they would reward the dog with a treat and then move on to the next one. But they could only continue approaching if the dog remained calm. Think of it as green light - go (dog is sitting and calm), yellow light - stop (dog is standing and starting to get excited), red light - back away (dog is whining or barking in excitement and/or flailing about). Yellow light means they have to wait until he calms down to continue approaching, red light means they have to increase distance so they're further away.
Although this starts out with impulse control around food, I've found it's a great game to play with puppies:
From food you can go onto toys, and there's no reason you can't use it with people too - have them stand still while you approach with him on leash, and either continue approaching them, stop and wait for calmer behavior, or back further away depending on his demeanor, as I described above.
Exercise is very important, but I think a lot of people don't also reinforce calm behavior enough. Just like any other behavior, you can teach a dog to calm down, to relax, to hang out and chill for awhile. Training a dog to go to a mat is great, and something you can easily start now. I wrote about it on this thread: Fun tricks to teach your puppy?
Remember that attention is very reinforcing so if he continues to get attention for inappropriate behavior there is no incentive for him to stop doing it. He needs to be managed so he can't behave badly when greeting people, while he gets tons of reinforcement for doing it right.