How do I make tank AI move better?

See more:

C#

artificial-intelligence

Unity

So I'm making an ai for a tank game but instead of the tank moving smoothly, it just skids around in one direction when it should be moving around the map independently as well. how do I fix this? Here is the code:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class EnemyTankMove : MonoBehaviour
{
    Rigidbody rbEnemyTank;

    float posX;
    float posZ;


    float posMin = 50f;
    float posMax = 50f;

    Vector3 targetPos;

    public float speedMove = 0.05f;
    public float speedRotate = 0.1f;



    void Awake()
    {
        rbEnemyTank = GetComponent<rigidbody>();
    }

    void Start()
    {
        GetNewPosition();
    }

    void GetNewPosition()
    {
        posX = Random.Range(posMin, posMax);
        posZ = Random.Range(posMin, posMax);

        Vector3 newPosition = new Vector3(posX, transform.position.y, posZ);
        targetPos = newPosition;
    }

    void Update()
    {
        if (Vector3.Distance(transform.position, targetPos) < 10f)
        {
            GetNewPosition();
        }
        Rotate();
    }

    void FixedUpdate()
    {
        Move();
    }

    void Rotate()
    {
        Vector3 tankDir = targetPos - transform.position;
        float step = speedRotate * Time.deltaTime;
        Vector3 newDir = Vector3.RotateTowards(transform.forward, tankDir, step, 0.0f);
    }

    void Move()
    {
        Vector3 moveForward = transform.forward * speedMove;
        rbEnemyTank.MovePosition(rbEnemyTank.position + moveForward);
    }
}

What I have tried:

nothing has worked, I need help but as I'm new to programming please be understanding.

Thanks!