Never experienced this...timidity with new people
I've had shepherds my whole life, first memory is crawling around Diamond when I was little little.
I've owned 2 before Odin, Gemini was neurotic and crazy, Rebel was dog aggressive but not aggressive otherwise.
Odin is nearly 6 months and in his own space barks incessantly when new people come into his territory--whether it's people approaching me when I'm standing near the car and he's in the car, or new people coming in to our house.
It's not aggressive, it's fear. He'll crawl up onto the furniture to get behind us and bark, bark, bark.
We've started working with it with new people being asked to just ignore him, or not look at him and drop treats or his ball for him. That seemed to work better than them trying too hard to make friends.
Other recommendations? He does pretty well out of his "zone" like in stores or outside in parks etc. But he gets a bit overwhelming when he starts in with the barking in the car or at home.
Chris, mom to:
Tank (Cardigan Welsh Corgi)
Odin (GSD 8/28/13)
Valentine-our ragdoll cat
Two great skin kids