Move forward + allow to step sideways.

This is likely an easy one. I can see the issue but am unsure what the most efficient way to fix it would be. I am basically making an endless run type prototype. I have the player moving forward on the z axis over time and when the space bar is pressed I want the player to move a distance to the left or right, but they movement in the update is conflicting.

I will include the script below. This script is attached to the player object.

 using UnityEngine;
 using System.Collections;
 using System;
 
 public class PlayerMove : MonoBehaviour
 {
 
     //////////////////////////////////////////////////////////////////////////////
     //                                                                          // 
     //Variables                                                                 //                
     //                                                                          //               
     //////////////////////////////////////////////////////////////////////////////
     public enum SIDE { Left, Right }
 
     static public PlayerMove instance;
 
     public float speed; 
 
     private Vector3 newPos;
     private SIDE side;
     private bool mbMagDown = false;
 
     private Vector3 moveVector = new Vector3(0, 0, 1);
 
     //////////////////////////////////////////////////////////////////////////////
     //                                                                          // 
     //Unity Functions                                                           //                
     //                                                                          //               
     //////////////////////////////////////////////////////////////////////////////
     void Awake()
     {
         instance = this;
     }
 
     void Start()
     {
         transform.position = new Vector3(-2.5f, 1.5f, 0);
         newPos = transform.position;
         side = SIDE.Left;
     }
 
     void Update()
     {
         // Move forward over time. 
         transform.Translate(moveVector * speed * Time.deltaTime);
 
         if (Input.GetKeyDown(KeyCode.Space))
         {
 
             if (side == SIDE.Left)
             {
                 newPos = new Vector3(2.5f, transform.position.y, transform.position.z);
                 side = SIDE.Right;
             }
             else
             {
                 newPos = new Vector3(-2.5f, transform.position.y, transform.position.z);
                 side = SIDE.Left;
             }
         }
 
         // SUPPOSED to move player to either side.
         transform.position = Vector3.Lerp(transform.position, newPos, Time.deltaTime * 10);
     }
 
     //////////////////////////////////////////////////////////////////////////////
     //                                                                          // 
     //Custom Functions                                                          //
     //                                                                          //               
     //////////////////////////////////////////////////////////////////////////////
 
 }