Player lag seriously when login

Hello,

I expected when players joined the server a custom welcome message will be sent to him/her. However, when I joined my server, the welcome message did not show. Then, I need to type a login command, but the server did not respond to the player’s command. After around 30 seconds, every message popped out at the same time.

Also, I have hosted some servers with this server provider but this was the first time the issue happened. I even tried to localhost with my powerful computer. There was still have around 15 seconds of lag.

Server specs:
Intel Core i7-6700 (I am not sure the CPU limit)
8GB DDR4 RAM
SATA SSD

This is my timing report: (Many red numbers)
https://timings.aikar.co/?id=203913a5f45143c39ddb0539f93badb7

Can anyone suggest some ways to fix this? I am not sure what is causing this.