Help on Player Movement Script C#

I have a problem with my script.When I have this script on my player and I put rigidbody on it and play the game and then I try to jump the cube freaks out and starts to flip flop evertywhere. Here is my script.

using UnityEngine; using System.Collections;

public class Movement : MonoBehaviour { //Variables Start

 //Public Variables
 public float PlayerSpeedWalk = 5.0f;
 public float PlayerSpeedSprint = 8.0f;
 public float PlayerSpeedCrawl = 3.0f;
 public float PlayerSpeedCrouch = 2.0f;
 public float PlayerJumpHeight = 2.0f;

 public bool IsSprint = false;
 public bool IsCrawl = false;
 public bool IsCrouch = false;

 //Private Variables

 
 //Variables End


 // Use this for initialization
 void Start () 
 {

 }
 
 // Update is called once per frame
 void Update () 
 {
     //Walking Movement
     if(IsSprint == false && IsCrawl == false && IsCrouch == false)
     {
         float moveX = Input.GetAxis("Horizontal") * PlayerSpeedWalk  * Time.deltaTime;

         float moveY = Input.GetAxis("Jump") * PlayerJumpHeight * Time.deltaTime;
         
         float moveZ = Input.GetAxis("Vertical") * PlayerSpeedWalk  * Time.deltaTime;

         transform.Translate(moveX,moveY,moveZ);
     }


     //Sprint Bool   
     if(Input.GetKeyDown(KeyCode.LeftShift) && IsSprint == false)
     {
         IsSprint = true;
     }
     
     else if(Input.GetKeyUp(KeyCode.LeftShift) && IsSprint == true)
     {
         IsSprint = false;
     }
     
     //Sprint Movement
     if(IsSprint == true)
     {
         float moveXS = Input.GetAxis("Horizontal") * PlayerSpeedSprint * Time.deltaTime;
         
         float moveYS = Input.GetAxis("Jump") * PlayerJumpHeight * Time.deltaTime;
         
         float moveZS = Input.GetAxis("Vertical") * PlayerSpeedSprint * Time.deltaTime;
         
         transform.Translate(moveXS,moveYS,moveZS);
     }


     //Crawl Bool  
     if(Input.GetKeyDown(KeyCode.Z) && IsCrawl == false)
     {
         IsCrawl = true;
     }
     
     else if(Input.GetKeyUp(KeyCode.Z) && IsCrawl == true)
     {
         IsCrawl = false;
     }
     
     //Crawl Movement
     if(IsCrawl == true)
     {
         float moveXCl = Input.GetAxis("Horizontal") * PlayerSpeedCrawl * Time.deltaTime;
         
         float moveZCl = Input.GetAxis("Vertical") * PlayerSpeedCrawl * Time.deltaTime;
         
         transform.Translate(moveXCl,0,moveZCl);
     }


     //Crouch Bool   
     if(Input.GetKeyDown(KeyCode.C) && IsCrouch == false)
     {
         IsCrouch = true;
     }
     
     else if(Input.GetKeyUp(KeyCode.C) && IsCrouch == true)
     {
         IsCrouch = false;
     }

     //Crouch Movement
     if(IsCrouch == true)
     {
         float moveXC = Input.GetAxis("Horizontal") * PlayerSpeedCrouch * Time.deltaTime;
         
         float moveZC = Input.GetAxis("Vertical") * PlayerSpeedCrouch * Time.deltaTime;
         
         transform.Translate(moveXC,0,moveZC);

     }

 
 }

}

I looked over other script and I dont see anything that could cause this problem.It might be because I am new to unity and to C#.

So I guess the thing I am asking is how do you fix this problem?