Barking at people
I have a 22 month old GSD who has starting barking at people he meets while walking. We got him at 6 months completely unsocialized. He had never been out of the pen at his breeder's before we got him as breeder was in bad health and was having trouble taking care of him. We were surprised at how friendly he was with people with such little previous interaction with people. He's been socialized a lot since that time and been in numerous training classes. He loved going up to people and getting petted when younger. When he turned 16 months and after being neutured, we noticed him being nervous around people he hadn't met. A few times he would go up to them and then back away and bark. We immediately put a halt to people petting him unless he initiated the contact and looked comfortable. Just recently, he's meet a few people he's known before on walks, walked up to them, got petted and then barked at them. We've spoken to our obedience trainer and was told to correct him when he does that. I'm worried there's something else going on and that a correction could be making it worse. He's barked at both men and women. Any suggestions?