Adapted from Philipp's answer. This will start and stop the coroutine as needed.

using System.Collections;
using UnityEngine;

public class ToggleableCoroutine : MonoBehaviour
{
    private Coroutine myCoroutine;

    void Update()
    {
        if (Input.anyKeyDown)
        {
            if (myCoroutine != null)
            {
                StopCoroutine(myCoroutine);
            }
            else
            {
                myCoroutine = StartCoroutine(MyCoroutine());
            }
        }
    }

    private IEnumerator MyCoroutine()
    {
        while (true)
        {
            Debug.Log("Coroutine is active");
            yield return new WaitForSeconds(1.0f);
        }
    }
}

Although I recommend using Async & Await, instead of Coroutines.

Adapted from Philipp's answer. This will start and stop the coroutine as needed.

using System.Collections;
using UnityEngine;

public class ToggleableCoroutine : MonoBehaviour
{
    private Coroutine myCoroutine;

    void Update()
    {
        if (Input.anyKeyDown)
        {
            if (myCoroutine != null)
            {
                StopCoroutine(myCoroutine);
            }
            else
            {
                myCoroutine = StartCoroutine(MyCoroutine());
            }
        }
    }

    private IEnumerator MyCoroutine()
    {
        while (true)
        {
            Debug.Log("Coroutine is active");
            yield return new WaitForSeconds(1.0f);
        }
    }
}

Although I recommend using Async & Await, instead of Coroutines: Should I use Async & Await, instead of Coroutines, in Unity?