Character Spin Issue

I'm making a game for Google Cardboard where the player can walk around and jump using the Cardboard Trigger. I'm having an issue with my player where it will start spinning automatically if I collide with something, but this problem doesn't happen every time. I just need a way to keep the player from spinning.

Walking Script:

 public class Walker : MonoBehaviour {
 
     public bool walking = false; //whether or not walking is enabled
     public float speed = 1.0f; //speed in units per second
     public Transform head; //attach the forward looking object
     
     void FixedUpdate () {
         if (walking) {
             Vector3 forwardNoY = new Vector3 (head.forward.x, 0, head.forward.z);
             forwardNoY.Normalize ();
 
             this.transform.Translate (forwardNoY * speed * Time.deltaTime, Space.World);
         }
     }
 
     public void toggleWalk(){
         walking = !walking;
     }
 }

Jumping Script:

 public class TriggerJump : MonoBehaviour {
 
     public bool grounded = true; //whether or not the player is on the ground
     public bool hasJumped = false; //whether or not jumping is enabled
     public float jumpPower = 10.0f; //speed in units per second
     public Transform body; //attach to the player object
     public Rigidbody rb;
 
     void Start () {
         rb = GetComponent<Rigidbody> ();
     }
 
     void Update () {
         if (!grounded) {
             grounded = true;
         }
 
         if (Cardboard.SDK.Triggered && grounded == true) {
             hasJumped = true;
         }
     }
 
     void FixedUpdate () {
         if (hasJumped) {
             rb.AddForce(body.up * jumpPower, ForceMode.Impulse);
             grounded = false;
             hasJumped = false;
         }
     }
 }