I've noticed that recently blood flow is more easily restricted in my left arm when bent. e.g. resting my head on my left hand while on desk. concern?

You are describing: symptoms of restricted blood flow, such as..? Numbness, tingling (like falling asleep) and pain can be associated with dependent position over long periods of time. It has to do with the nerve being compressed or overstimulated. If you have recurrent purple or blue hands, even without prolonged pressure on them, you need to get checked out by healthcare provider