No that is not normal. Well at least not for a healthy well bred sheltie. However many of the shelties that come from puppymills or back yard breeders tend to be really skittish.
The sheltie standard says that the breed should be reserved, which many people interpret incorrectly to mean that they should be shy.
Do you know much about his background, and how he's been raised so far?
If he were my dog I would start socializing him as much as possible. I would encourage him to go up and investigate whatever it is that startles him. Don't react to him when he startles at something, just ignore him.

As for his height, well it is common to have size variations in shelties. The standard says they are supposed to be between 13" and 16" tall, but they don't breed true to type as they are a fairly new breed (in the grand scheme of things). Both of my shelties are over-sized. His coat is probably normal for an 8 month old pup. Emily didn't have a full coat until she was about 2 years old.

Hope what I've told you helps. Feel free to ask if you have any other questions.