Numbness in the arm after waking up in the morning depends on how long it has lasted.
If the numbness disappears after a short period of time or after moving the arm, it is not usually due to a medical condition, but may be due to nerve compression in the upper limbs as a result of poor sleeping posture.
If the numbness persists for a longer period of time and does not resolve, then it is important to consider the presence of a medical condition.