you could enable persistent logging to have some log after next reboot
persistent system logs:
[code]
dietpi-software uninstall 103 # uninstalls DIetPi-RAMlog
mkdir /var/log/journal # triggers systemd-journald logs to disk
reboot # required to finalise the RAMlog uninstall
[/code]
Then you can check system logs via:
[code]journalctl[/code]
which will then show as well logs from previous boot sessions. To limit the size, you can additionally e.g. apply the following:
[code]
mkdir -p /etc/systemd/journald.conf.d
cat << '_EOF_' > /etc/systemd/journald.conf.d/99-custom.conf
[Journal]
SystemMaxFiles=2
MaxFileSec=7day
_EOF_
[/code]
This will limit logs to 14 days split across two journal files, so that with rotation you will always have between 7 and 14 days of logs available.
if possible, have a look to memory usage. Probably your system is running out of physical memory, causing system to swap. At least an explanation for disk usage and paging.