How to remove character jerking against other vertical colliders?

Question

Unity

When a character collides with another collider, it starts to twitch (specifically with a vertical one, such as walls).
It seems to me that this is a very simple question, since I have already seen similar topics on this forum. But I will tell you that I am a complete newbie in the field of units and programming in general, so please explain everything to me on the fingers of what and how.
Character config (on the character there is a collider and Rigidbody 2D, and only a collider on the wall):

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(Rigidbody2D))]

public class Player2DControl : MonoBehaviour
{

  public enum ProjectAxis { onlyX = 0, xAndY = 1 };
  public ProjectAxis projectAxis = ProjectAxis.onlyX;
  public float speed = 150;
  public float addForce = 7;
  public bool lookAtCursor;
  public KeyCode leftButton = KeyCode.A;
  public KeyCode rightButton = KeyCode.D;
  public KeyCode upButton = KeyCode.W;
  public KeyCode downButton = KeyCode.S;
  public KeyCode addForceButton = KeyCode.Space;
  public bool isFacingRight = true;
  private Vector3 direction;
  private float vertical;
  private float horizontal;
  private Rigidbody2D body;
  private float rotationY;
  private bool jump;

  void Start()
  {
    body = GetComponent<Rigidbody2D>();
    body.fixedAngle = true;

    if (projectAxis == ProjectAxis.xAndY)
    {
      body.gravityScale = 0;
      body.drag = 10;
    }
  }

  void OnCollisionStay2D(Collision2D coll)
  {
    if (coll.transform.tag == "Ground")
    {
      body.drag = 10;
      jump = true;
    }
  }

  void OnCollisionExit2D(Collision2D coll)
  {
    if (coll.transform.tag == "Ground")
    {
      body.drag = 0;
      jump = false;
    }
  }

  void FixedUpdate()
  {
    body.AddForce(direction * body.mass * speed);

    if (Mathf.Abs(body.velocity.x) > speed / 100f)
    {
      body.velocity = new Vector2(Mathf.Sign(body.velocity.x) * speed / 100f, body.velocity.y);
    }

    if (projectAxis == ProjectAxis.xAndY)
    {
      if (Mathf.Abs(body.velocity.y) > speed / 100f)
      {
        body.velocity = new Vector2(body.velocity.x, Mathf.Sign(body.velocity.y) * speed / 100f);
      }
    }
    else
    {
      if (Input.GetKey(addForceButton) && jump)
      {
        body.velocity = new Vector2(0, addForce);
      }
    }
  }

  void Flip()
  {
    if (projectAxis == ProjectAxis.onlyX)
    {
      isFacingRight = !isFacingRight;
      Vector3 theScale = transform.localScale;
      theScale.x *= -1;
      transform.localScale = theScale;
    }
  }

  void Update()
  {
    if (lookAtCursor)
    {
      Vector3 lookPos = Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, Camera.main.transform.position.z));
      lookPos = lookPos - transform.position;
      float angle = Mathf.Atan2(lookPos.y, lookPos.x) * Mathf.Rad2Deg;
      transform.rotation = Quaternion.AngleAxis(angle, Vector3.forward);
    }

    if (Input.GetKey(upButton)) vertical = 1;
    else if (Input.GetKey(downButton)) vertical = -1; else vertical = 0;

    if (Input.GetKey(leftButton)) horizontal = -1;
    else if (Input.GetKey(rightButton)) horizontal = 1; else horizontal = 0;

    if (projectAxis == ProjectAxis.onlyX)
    {
      direction = new Vector2(horizontal, 0);
    }
    else
    {
      if (Input.GetKeyDown(addForceButton)) speed += addForce; else if (Input.GetKeyUp(addForceButton)) speed -= addForce;
      direction = new Vector2(horizontal, vertical);
    }

    if (horizontal > 0 && !isFacingRight) Flip(); else if (horizontal < 0 && isFacingRight) Flip();
  }
}