Foot numbness in the morning is primarily caused by conditions that interfere with the supply of blood to the foot. Some of these causes include diseases like the Degenerative Disc Disease and Sciatica, Leprosy, Multiple Sclerosis, and Peripheral Neuropathy, or Frostbite and Cold Weather-Related Injuries. Therefore, it is important to seek medical help once you experience any form of numbness in the morning, because they may be due to some underlying complex medical condition.
Could be the position you are sleeping in. My arm was that way in the mornings and I started to realize in the morning when I woke up I was sticking my arm under my pillow. With the weight of my head and the odd position of my arm it was making my arm fall asleep.