Hey,

when initializing a player (EntityPlayer) a new random-spawn position inside the world-spawn-area will be determined. To do this world.q(...) will be called causing chunks inside the spawn-area to be loaded. As a EntityPlayer Object will be created on each login-request (even if not successful) this happens very often.

It does not matter if the player has been on the server before. The code in the consctructor will be called before updating with the saved playerinformation