Juvenile Onset Shyness

Have any of you had a dog that has begun to exhibit signs of fearfulness or shyness after 6 months? I'm curious about Juvenile Onset Shyness, quite common in many dogs. With the proper socialization and training, many outgrow this. I think Noel has experienced this although at the time I wasn't sure what exactly was going on. She was a very outgoing friendly puppy, extremely well socialized, but around one year started showing signs of mild fearfulness in certain situations and greeting people. She recovered quickly in most situations so she wasn't an extreme case. Now at almost two and a half she seems to be getting back to her old self again, confident and outgoing, which of course I am happy and relieved to see.