Vasovagal Syncope: This condition is characterized by a sudden drop in blood pressure, heart rate, and blood flow to the brain, often triggered by stress or pain, which could explain the near syncope events. The numbness/tingling in arms and hands could be related to the decreased blood flow, and the "locking up" of hands might be due to transient ischemic episodes affecting motor control.

Anxiety or Panic Disorder: These conditions can cause symptoms that mimic near syncope, including numbness/tingling sensations due to hyperventilation and muscle tension, which could lead to feelings of limbs "locking up."
Carpal Tunnel Syndrome or Other Entrapment Neuropathies: Direct compression of nerves can cause numbness, tingling, and weakness in the hands, potentially leading to a sensation of the hands "locking up."
Hypoglycemia: Low blood sugar can cause a range of symptoms including dizziness, confusion, and numbness/tingling in extremities, which might be perceived as near syncope and limb dysfunction.

Cardiac Arrhythmias (e.g., Atrial Fibrillation, Ventricular Tachycardia): These conditions can lead to reduced cardiac output, resulting in decreased blood flow to the brain and extremities, causing near syncope and neurological symptoms.
Transient Ischemic Attack (TIA) or Stroke: Although less common, TIAs or strokes can present with sudden onset of neurological deficits, including numbness/tingling and motor weakness, which could be mistaken for other conditions.
Multiple Sclerosis: An autoimmune disease affecting the central nervous system, which can cause a wide range of neurological symptoms including numbness, tingling, and weakness, potentially mimicking the described symptoms.

Peripheral Artery Disease: Although more common in the legs, severe PAD in the arms could potentially cause symptoms of decreased blood flow, including numbness and tingling, especially during exertion.
Neuromuscular Junction Disorders (e.g., Myasthenia Gravis): These conditions can cause fluctuating muscle weakness, which might be perceived as limbs "locking up," especially after periods of activity.
Mitochondrial Myopathies: A group of disorders affecting the mitochondria, leading to muscle weakness and neurological symptoms, which could potentially include the symptoms described, though this would be a less common presentation.