What Does Dull Shoulder Pain With Tingling In The Hands Indicate?

Good afternoon. Recently I have been experiencing shoulder/neck ache with tingling down my arm to my fingers on my left side. I am right handed. I am very active. I am 61 years old. I work behind a desk. I play racquetball right-handed a couple of times per week, swim daily, bike and run a couple of times per week. As I sit at my desk (later in the morning), I get a dull achy pain that starts at the top of my left shoulder into my neck. The pain works its way down my arm and includes a slight tingling in my left hand to my fingers. This only happens when I am sitting and at rest. If I get up and walk around, or shift my sitting position, the pain tends to go away. The achy pain is fatiguing if that makes sense???