I've been having a tingling sensation on my left shoulder blade for some time. it isn't numb, but it tingles, sometimes more than others. dangerous?

Likely benign: Probably it is due to irritated or pinched nerve in neck or thoracic spine. If persistent for a few months then see a neurologist.

Do you have pain: Do you have pain in neck or back? Any difficulty breathing? Have you ever had shingles? If the answer to these are no, then it is less likely to be dangerous, but consult with us or see your MD to do a full neuro exam.