2D Random AI

I put together a little simple example for you. I assumed boundaries but if you tell me more what exactly the condition is where your AI shouldn't move anymore I could help your further. Hope it helps :)

 //wall Boundaries
     float wall_left   = 5.0f;
     float wall_right  = Screen.width  - 5.0f;
     float wall_top    = Screen.height - 5.0f;
     float wall_bottom = 5.0f;
             
     //AI properties
     Vector2 AI_Position;
     float Speed = 0.3f;    
     
     //Get two Random values within a Range (Screen dimensions)
     float randomX = Random.Range(0,Screen.width);
     float randomY = Random.Range(0,Screen.height);
     
     //Create a Vector2 out of the Random values
     Vector2 randomXY = new Vector2(randomX,randomY);
     
     //Get the Direction from AI to the RandomXY generated
     Vector2 Direction = randomXY - AI_Position;
     
     //Normalize the Direction to apply appropriatly
     Direction = Direction.normalized;
     
     //Check that your AI is within your boundaries
     if(    AI_Position.x > wall_left && AI_Position.x < wall_right
         && AI_Position.y > wall_bottom && AI_Position.y < wall_top )
     {
     //Make AI move in the Direction (adjust speed to your needs)
         AI_Position += Direction * Speed;
     }
     else
     {
     //make your AI do something when its not within the boundaries
     //maybe generate a new direction?
     }