I experienced some crashes what I believed was during saves of the world. Therefore I thought it might be a smart idea to save more often, so that saves aren’t as big.
I went into the WebUI and changed it from 60 to 5 minutes, but then realized that the 60 was greyed out. Since that change I get saving world notices both in console and in Minecraft chat every 5 minutes. Those weren’t there before at all. As I understood, Minecraft Servers should save automatically every 5 minutes, so I don’t really understand if I double save every 5 minutes etc.
However, that still happens, but seems to only happen when people are on the server, the amount of people somewhat corresponding to the amount of crashes.
When the server crashes it tells me that it can’t find the start.sh file, to automatically restart the server. Didn’t find really good information on that (for example in which folder that script should be etc.), so hoping to get some help from you on that part, too.
Installed Spigot plugins:
bpermissions
CBSuicide
Dynmap (3.0 Beta)
Dynmap GriefPrevention
FastLeafDecay
GriefPrevention
SetHome
Server logs of 2 Crashes
https://pastebin.com/baCrQpwe
https://pastebin.com/W3T91WnM
Appreciate any help 
==========Addition===============
The machine is a Fujitsu Esprimo with an Intel Core 2 Duo and 4½ Gb of RAM
The minecraft server software should automatically savce your world to disk every 5 minutes. This is a server internal process, and is not notified ingame
When you tell MineOS to trigger a save, you are really telling MineOS to run the /save command in-game. This command is an admin or operator command, and is notified ingame.
The reason MineOS has the ability to trigger saves is because there has been some instances of buggy minecraft servers not saving normally. You can therefore tell MineOS to trigger a manual save at periods.
Minecraft also saves automatically whenever a player quits.
As for your crashes:
Seems like they may be tied up in one or more of your plugins. To find what plugin crashes your server I advice you to disable each plugin. Try to run your spigot without any plugs to rule out any spigot crashes. If that works fine, then activate one plug at a time and start the server to see if that plug causes the crash. When you find the guilty plug, report it to the plugin author.
[18:48:39] [Server thread/WARN]: **** SERVER IS RUNNING IN OFFLINE/INSECURE MODE!
I can also see that you run your server in with the “offline” setting. This is not reccomended, since this makes it really easy to spoof a player-name. The only reason to run “offline” is to allow pirated clients. Online just means that your server chekcs usernames against Mojangs login-Servers.
This is the reccomended settings for security:
online-mode=true
white-list=true
This means that all users usernames is checked against Mojangs login-servers. this means a username is secured and harder to spoof. With whitelist you also only allow in those players you want to grant access.
Without online-mode=true, anyone can assume a username and log on, automatically getting all the rights you have granted that username either as OP, or via the bPermissions-plug.
Thanks for shedding light on the saving situation.
I am aware of the Offline Mode situation and dislike it, too. But friends are friends and not all have the same view about Piracy.
I will then try with the disabling of plugins, but since crashes occur approximately once a day, I guess the other players won’t be to happy about it 
Thank you very much for your help.
If you (Or someone else) could help me with the restart script, that would also be much appreciated, as it’s not a huge deal if the server dies and restarts for a couple of minutes, but a day or so until I notice is unfortunate.