To disable watchdog timers (both software and hardware), append nowatchdog to your boot parameters.
e.g. sudo nano /etc/default/grub
add nowatchdog to the kernel line like so:
GRUB_CMDLINE_LINUX_DEFAULT="quiet nowatchdog ..."
save [ Ctrl+X ]
rebuild grub.cfg:
sudo grub-mkconfig -o /boot/grub/grub.cfg
reboot