I have an 11 year old Miniature Schnauzer and he's pretty shy and fearful of new people (men more than women). He can be aggressive at times, lunging or biting at people when he seems to think they are too close to me. He'll even nip at my family members when they do something harmless like hug me. As he has gotten older, the issue seems to have gotten worse. How can I help combat this behavior in a dog his age? I know professional training is the obvious answer, but I cannot afford to do that. How can I make things a bit better on my own?