Failed to call hook 'OnPlayerSleepEnded' on plugin 'GUIAnnouncements v2.0.3' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.GUIAnnouncements.OnPlayerSleepEnded (BasePlayer player) [0x00014] in <ea3b122520d44e0bac8a017ba621112b>:0 
  at Oxide.Plugins.GUIAnnouncements.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00892] in <ea3b122520d44e0bac8a017ba621112b>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <80b90e8213db44b29ec2d4111764172c>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <ec05e0208c9149bba43236ca58fea105>:0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <ec05e0208c9149bba43236ca58fea105>:0  

Who what when where why how?

Or in other words:

What else is in your console?

Did a player join at that time?

Did a player already in the server stop sleeping? Perhaps after a teleport?

Do you have any other plugins?

Has it affected the functionality of anything?

Or is this just an error that popped up with seemingly nothing happening in game?

Can you recreate it?

JoeSheep

So you get this before anyone connects? It's not triggered by someone connecting?

Yeap, it shows up after my server load up completely.

Stop the server. Delete the data file. Start it up. See if that stops it.

Do you have any other plugins?
Has it affected the functionality of anything?
What else is in your console?