It usually happens when server is idling, but I've also seen it happen in the middle of a conversation. Server is not crashing. When it happens logs show nothing, even in debug mode.

send your log

Ok... I'm a moronne. I had another test server which had crontab @reboot rule that also started minecraft. It was in disarray and kept crashing so all of those "Server has started" was from that other server.

Thank's for that last message. I'd probably still be clueless without it.

There you go:

debug enabled

some marks to know when it happened

log itself
2020-08-28-4.log.gz

run /discord debug & paste the url here

https://bin.scarsz.me/db7481ba-9703-483f-b1e4-d9f8cd830dec#B5jiohxoa845j3YiUgOPdeXXu2h4il0s

First time i've ever seen anything like this, the only time DiscordSRV sends the server has started message is when the plugin is enabled.