Anxety paralysis
There are two reasons that this occurs. The first is hyperventilation. Hyperventilation is the act of breathing out too much carbon dioxide, so that your body responds by slowing down blood flow to certain areas of your body. This is what causes it to feel as though certain body parts can't move. They may start to tingle or feel numb, causing you to feel as though your muscles aren't working. Hyperventilation is triggered by anxiety; and it may maintain or worsen your anxiety as well.
The second issue is a bit more complex. Our bodies perform many movements automatically. These include, for example, blinking, swallowing, smiling or moving out of the way of an approaching vehicle. Your mind sends signals down your nerves for how to move, and you move them. When you walk, even if you are thinking about walking, you generally don't focus on literally each muscle movement one at a time. Walking - like all movements - are unconscious and controlled by your mind.
When someone suffers from anxiety, they often focus deeply on the way their body feels, becoming highly attuned and conscious of movements which would otherwise be performed spontaneously and automatically. The process of actively contemplating the series of movements that you’re performing may interfere with the automatic process whereby those actions would normally be carried out. This may make automatic movements harder to perform, creating a sense of immobilization.
Imreally liked finding this, it describes how i feel , i know i cna move, i know im healthy and nothing is wrong but my excess supervision on my body and watching every little detail and change made me feel like i forgot the ability to feel and i seriously feel numb , like when i move my arms and legs it feels weird like they are moving by their own, although i feel i have no control i know i do, i watch for every movement and its becoming non automatic, like i have to watch every muscle and bone and nerve in my body ...i know it wont last long and soon will feel better i just need to calm and remind myself i have been through alot but never have i not gotten over it and felt much better