OnTriggerEnter2D works without being actually triggered.

I am working on a simple enemy spawn system. I have a game object with a Circle Trigger attached with the tag "SpawnArea". Whenever the enemy walks into it, I want to flip it's direction. Here is what I have added to my enemy_move script:

 void OnTriggerEnter2D(Collider2D col){
         Debug.Log ("collision");
         if(col.CompareTag("SpawnArea")){
             Debug.Log("wall collision");
             this.transform.Rotate (Vector3.forward * -dir);
             timer = stopTime;
         }

As you can see I am using the debugger to log errors. As soon as I run the game (even though my enemy is far away from the Circle Collider), I get both the logs appearing in my console even though there is no collision. Then the enemy doesn't detect the Collider further and continues moving on. I have checked everything. The Circle Collider is a trigger, my enemy has a rigidbody attached. They are all on the Default layer, the z value of each is the same. I don't understand why this is happening. Please help! thanks!!

(I have also tried OnCollisionEnter2D)