When you create or connect to a world on Minecraft Windows 10 Edition. You keep constantly sprinting and you will not stop. Even when you are standing still. I know this because when you stand still you can see the sprinting particles below you.
Linked issues
Comments 2
duplicate of
https://bugs.mojang.com/browse/MCPE-9807
I have the problem as well. if you run into a block it helps. I am saying this so we can wait for the update.