bool changing on its own?

I'm making a game where I want the player to turn when it gets too far to the side. To do this I created a coroutine named "nearWalls" which controls the turning. I'm using the bool "nearWall" to prevent the coroutine from constantly being run over and over again since I only want it to be run once. However, when the if statement is satisfied, the bool keeps changing from true to false. I'm really confused as to why the bool keeps changing since to me it looks like it should only ever change once after the application runs, which is when the if statement is satisfied. Any help would be appreciated, thanks!

 public class Froggy : MonoBehaviour {
 bool nearWall = false;
 
 void Update () {
         Debug.Log ("the nearWall bool is: " + nearWall);
 
 if (transform.position.x >= 13f || transform.position.x <= -13f) {
             if (nearWall == false) {
                 nearWall = true;
                 StartCoroutine (nearWalls ());
             }
 }
 IEnumerator nearWalls(){
 //nothing changing the nearWall bool
 }
 }

Before if statement is satisfied:

After if statement is satisfied: