Help with rigidbodies and follow transform

Hello, so I have been experimenting with basic A.I systems in unity and I put together a bit of code that seems to work alright.

My dillema is that I want the enemy to follow my player and collide with objects while doing so, for example: when moving towards my player I want it to colide with a small hill/bump infront of it.

To do this I added a rigidbody and a box collider (I tried each collider) and now it will collide with objects, but instead of following it will bounce around randomly, maybe fly off into the air or go backwards.

Does anyone have a way to fix this?

 var target : Transform;
 var speed : float = 3;
 private var fixedCoordinate : int = 0;
 var follow : boolean;
 var lookAt : boolean;
 function Update()
 {
     if(Input.GetKeyDown(KeyCode.F))
     {
         follow = true;
     }
     if(Input.GetKey(KeyCode.R))
     {
         lookAt = true;
     }
     if(lookAt)
     {
     transform.LookAt(Vector3(target.position.x, fixedCoordinate, target.position.z));
     }
     if(follow)
     {
         this.transform.Translate(Vector3.forward * speed * Time.deltaTime);
     }
 }

if anyone has a fix for this that would be great! Thanks!