The collision capsule inside the pawn is colliding with the ground, but if your skeletal mesh is bigger than the collision capsule, then you need to compensate for that.
First I strongly suggest you to add collision capsule so that the entire skeletal mesh will be inside them, otherwise you’ll end up clipping with most of the body inside something that you should collide with.
Second use tracing to manage the height of your skeletal mesh, by using IK or Spine//Fabrik nodes inside ABP/Control Rig.
I’m not sure which one could work for you, since I don’t know if your skeletal mesh is a snake, mechanical mesh, or something like that, but using tracing should solve your issues and take into account the height difference for the front/back body parts.