After being awake for a couple hours this morning I developed a pain in my left shoulder. It has been constant for at least 6 hours. There is a stabbing pain every time I move, breath, bend or twist. I have taken ibuprofen and used a cold pack on it and the pain still hasn't let up. I have not done any strenuous physical activities. It was fine when I woke up and then it started hurting almost out of nowhere. What could be wrong? Do I need to see a doctor?

Definitely see a doctor. You could have just slept on it wrong but there are serious things that should be immediately checked out such as potential heart attack or blood clot. There is also a condition called costochondritis (which I've likely misspelled) that can hurt like hell - I've had several bouts of it myself and had never heard of it before though it's apparently pretty common. It can cause chest pain, which in my case seemed to be radiating from my shoulder into my chest wall and felt like what you are generally describing. I didn't know what was going on when I had my first attack but thought I was going to die. It's, I guess, related to arthritis and it did resolve.

It sounds like you're in a lot of pain, so go to the emergency room or urgent care today. Sudden pain like that occurs without any knowledge of being injurred should always be checked out immediately. It's probably nothing serious, but always better safe than sorry.

It could be a pinched nerve (as well as heart problem). If the ER finds nothing, find a GOOD chiropractor.
Also you don't want cold. Cold is for swelling only. You want moist heat, a pad with a washcloth, or a bath or shower. Gently move your neck and arm in the warm water to see if it lessens. It's possible that it will go away on it's own with all that.