Random Running and Follow at Certain Distance

Hi, so I'm making a game and I want to have an enemy run around the map (in the middle too) without a particular waypoint, just running all over. And once the player is within a certain distance it will start chasing the player. Any help or suggestions would be nice. I have a good understanding of the unity interface. I understand the basics of waypoints but I want it to be random not specific. But all over the map if possible. Thanks