I have problems with my 32gb thinkpad x13 gen 1 that sounds what you have and may be related to this.
What I did as a temporary solution is revert to an older kernel.
sudo qubes-dom0-update --action=install kernel-510
eddit: the 510 kernel
Then patching grub to allow me to select it at boot up
sudo grub2-mkconfig -o /boot/grub2/grub.cfg
Haven’t had any crashes in two days now except once when I forgot to select the older kernel.