Seems to happen without fail, here's a strack trace. https://paste2.org/yhBbmDsV PaperSpigot 1.12.2 https://timings.aikar.co/?id=0da7b1519a964910992540f245cf3be0
I would suggest making a copy of the server and run it locally(or on the remote server if you dont have any active players) and disable all plugins and re-enable them one by one to see wich plugin is causing it.
Get more ram. Get more CPU's. Get more TACOS!!! Tacos are key in any success of a server. (I agree with @DarkEyeDragon but if you are actually running low speced hosting I suggest getting at least 8gb of ram per 30 plugins with 20 players, that's streching it tho.)
