How to train and correct a soft GSD?

I have a 1 year old German Shepherd, and if I even give him a slight verbal correction like "uh-uh" it is enough to make him cower and urinate. I have had him since he was a puppy, and he has never been abused or in any tramatic situation that I know of. He is good on basic commands, like sit, stay, down, and come, but if I even go to grab his collar, he will cower and urinate. I have no idea how to really correct him because of the urination and fear he shows. I would love to be able to work with him without him cowering and urinating every time something slight startles or scares him. The constant urination is very annoying. How can I make it stop?