Both types of nerve cells have coatings surrounding them called myelin. However, motor nerves have thicker and more sensitive myelin layers. Now let's get back to the subject of sleeping feet. When a nerve cell is starved of oxygen, it stops working. Motor cells, with their thick myelin layers, are the first to stop working.
Sensory nerves stop next.
We rarely notice when this happens because our nerves are not awake enough to tell us when something is going wrong. However, when we roll over and return the blood flow, that's when we start to notice what's happening. As I said, some nerve cells are more sensitive than others. Since they send messages about pain and heat, our body interprets their waking-up as a burning sensation. That's what the pins and needles are all about.