Попробуйте так:
using UnityEngine;
public class MyAnimScript:MonoBehaviour
{
private Vector3 _lastPos;
void Start()
{
_lastPos = transform.position;
}
void Update()
{
var pos = transform.position;
if (_lastPos!=pos)
animation.CrossFade ("Run");
else
animation.CrossFade ("Idle");
_lastPos = pos;
}
}