I think temperament issues are a mix of genetics and human error. I have seen well bred dogs that were made into basket cases by thier owners...and poorly bred dogs that were very confident critters. But, I won't go into all that.
How have you been with your dog? When your dog acts fearful, what do you do? Most people anthropomorphize thier dogs...meaning they put human emotions into thier dogs. If your child is frightened, you get down, cuddle them and tell them it's OK... dogs do not think that way... if your dog is scared and you react the way you would with a child, you are reinforcing the fear and telling the dog it's OK to be fearful. What you should do if your dog acts fearful is either A. ignore the behavior B. redirect your dogs attention (obedience moves, etc.) It will take time... have some friends/aquaintences help you.... recreate a fearful situation... work your dog in OB from a distance...as he responds, slowly bring him in closer to the action, all the while keeping his focus on you...ignore any fearful responses..only praise when your dog performs well and with confidence. You need to feel confident yourself..going through the motions but fearing anxious on the inside will show through in your posture and actions, thus, setting your dog up to fail. Stay confident, be consistent, and your dog should do much better.
Now, if he is genetically weak, he may never be 100%, but any work you do now and from now on should make your dog a much more confident, easier critter to be around.