i cant tell if unity is glitching for me

Hello all, i have a problem with unity. so basically i am using unity 4.3's 2D feature to make a simple very small platformer. i imported my sprites and added collision to them and i added a rigid body to the main character. i tested the game out and it was fine. everything was going fine until i went to the codeing part, this my first time using c# im a complete beginer. i wrote a very simple move script: using UnityEngine; using System.Collections;

public class CharacterMovement : MonoBehaviour {

 // Use this for initialization
 public float PlayerSpeed = 5.00F;

 void Start () {
     transform.position = new Vector3 (1, 2, 0);
 }
 
 // Update is called once per frame
 void Update () {
     transform.Translate (Vector3.right * Input.GetAxis("Horizontal") * PlayerSpeed);
 
 }

}

i tested the game out for the first 5 seconds it was fine then ramdomly the main character just randomly started moving about without me touching the keyboard and then stops colliding. i go left the player goes right. i dont understand if it is a glitch or not, please help.

Thank You