Cervical Radiculopathy: This condition, often due to a herniated disc or bone spur in the cervical spine, can cause shoulder pain that radiates down to the fingers, accompanied by tingling sensations. The symptoms match closely with what is typically seen in cervical radiculopathy, making it a strong candidate for the single most likely diagnosis.

Thoracic Outlet Syndrome (TOS): TOS involves compression of the nerves and/or blood vessels that pass into the thoracic outlet (the space between your collarbone and first rib). This can cause shoulder pain, tingling in the fingers, and other symptoms that align with the described condition.
Brachial Plexus Injury: Although the question specifies "no injury," minor or unnoticed trauma could potentially cause a brachial plexus injury, leading to the described symptoms. This diagnosis should be considered, especially if there's any possibility of recent strain or overuse.
Referred Pain from the Neck: Musculoskeletal issues in the neck, such as strain or poor posture, can refer pain to the shoulder area and cause tingling sensations in the fingers due to nerve irritation.

Cervical Spinal Stenosis: A narrowing of the spinal canal in the neck, which can put pressure on the spinal cord and nerves, leading to pain, tingling, and potentially serious neurological deficits if not addressed.
Pancoast Tumor: A type of lung cancer located at the top of the lung that can invade nearby structures, including nerves, causing shoulder pain and tingling in the fingers. Although rare, missing this diagnosis could have severe consequences.
Stroke or Transient Ischemic Attack (TIA): While less common, sudden onset of shoulder pain with tingling in the fingers could be a manifestation of a stroke or TIA, especially if accompanied by other neurological symptoms.

Multiple Sclerosis: An autoimmune disease that affects the brain and spinal cord, potentially causing a wide range of neurological symptoms, including pain and tingling.
Peripheral Neuropathy: Damage to the peripheral nerves can cause tingling and pain in various parts of the body, including the fingers, though it would be less common for this to be directly related to shoulder pain without other symptoms.
Complex Regional Pain Syndrome (CRPS): A chronic pain condition characterized by severe, burning pain at the site of an injury, though the question specifies no injury, making this less likely.