Server lag issues?

On my Minecraft server every 5 minutes and 3 seconds I get the error on the server chat that the server can’t keep up, is the system overloaded apparently?

Error like running behind X ticks and so on and ONLY when I (the server host) is online on the server. My friends played for four hours without an once of trouble or lag and when I log on it all the sudden will freeze every five minutes. Any help would be GREATLY appreciated.