How to stop rigidbody from slowing down ?

Hi, So I'm making an infinite runner, this is my code and i used math.clamp to stop my car to go left and right and when it's reaching the limit(touch it) it slows down how do i stop it from doing that? here is my player_mover code

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class PlayerMover : MonoBehaviour {
     private Rigidbody Player;
     public float limit = 5f;
     public int speed = 6;
     public float forwardMovement = 1;
     public float leftAndRight = 1, upAndDown = 0, enableForward = 1;
 
     void Start () {
         Player = GetComponent<Rigidbody>();
     }
     void FixedUpdate() {
         // multipliers will say which axis will have more effect than other .. and disable the axis that is multiplied by 0
         Vector3 movement = new Vector3(Input.GetAxisRaw("Horizontal") * leftAndRight, Input.GetAxisRaw("Vertical") * upAndDown, forwardMovement * enableForward);
         // normalizing to 1 and moving
         movement = movement.normalized;
         Player.velocity = movement * speed ;
         // setting position bounderies using clamp on x axis 
         Player.position = new Vector3(Mathf.Clamp(Player.position.x, -limit, limit), transform.position.y, transform.position.z);
     }
 }