This sounds perfect for an “Idle/Run Blendspace”! They’re pretty standard for this sort of thing, it’s almost necessary for a slow down if you don’t have an actual “slowing down” animation.
If it only has a forwards movement, you can just use a Blendspace1D with 2 anims, idle at 0 and run anim at wherever you want, then plugging in “velocity” as your float input. That way it’ll auto-blend up and down based on distance from 0. 
