What makes your foot fall asleep?That tingly feeling is your nerves waking up.

From the show

Science Around You

That strange, prickly feeling when a limb 'falls asleep' is actually a good sign. When you sit in an odd position, you can temporarily compress a nerve, causing it to go numb. The 'pins and needles' you feel upon moving is the nerve waking up. As it comes back online, it sends a blast of chaotic signals to your brain. This tingling sensation is simply your nerve rebooting.