A feeling of weakness in one hand at night, with preserved finger movement, is most commonly due to nerve compression related to posture during sleep. Causes can include cervical spine (neck) nerve compression, ulnar or median nerve compression (from elbow or wrist position), or early cervical spondylosis. True neurological weakness is less likely if daytime function is normal.
Next Steps
Start with a physician or neurologist consultation. If neck pain, tingling, numbness, or radiation to the arm is present, a neurology or orthopaedic (spine) specialist is appropriate.
Health Tips
Avoid sleeping on the affected arm, keep the neck in neutral position, and use a proper pillow. Limit prolonged mobile or laptop use before bed. If you notice progressive weakness, numbness, hand clumsiness, facial deviation, speech difficulty, or symptoms during the day, seek urgent medical care.