I'm experiencing this problem since I installed Lubuntu on my ThinkPad L530 from Lenovo, in june 2023.
It was Lubuntu 22.04 LTS initially.At first the computer froze (generally after 7 days without restarting the PC), and I had a popup in my bios saying "the non volatile variable is about full, press F1 for settings", and had to save the changes (even tho I didnt do any), and then flush the content of efivars starting with dump-*
I thought it happened because the variable was progressively accumulating dumps so I made a cronjob to clean them every minute. No success, it still happened in the exact same manner, after some days, generally 4-7.
I got bored of this problem so I reinstalled in MBR mode and disabled EFI from the bios.
I still get the freezes but this time it's not mentioning any memory being full in the bios, it just freezes and I have to reboot.
I got suspicious about the version 22.04 and upgraded the pc to 24.04 LTS with the latest Linux kernel.
I still get the freezes, in the same manner: after some days not doing a full reboot, some minutes after my laptop goes out of sleep mode, it freezes.
I also played with some settings in the bios about sleep mode with no success.
What I can tell is the PC was not overheating, it was even colder than usual because it was just after going out of sleep mode.
The ram was not full, I was not doing anything special, just basic utilisation of my PC. Swap was also very far from being full, the laptop has 12 GB of RAM and 6 GB of Swap on an SSD.
The SSD is clean, checked with GSmartControl and smartctl.
I even replaced it with another one after cloning the disk with dd and it still happens
Quite frankly, I'm losing hope, and maybe it's the pc itself I can't tell for sure
Edit: now the system doesn't just freeze but performs a reboot after it freezes for some seconds.