Boot problem with Kubuntu 23.10

Hi all,

Long story as short as possible:

Lenovo Ideapad 3. I had windows 11 on SSD. Installed Ubuntu on HDD, dual boot with windows on SSD. Later decided I like Linux, no need for Windows. Installed Kubuntu on the SSD. Worked fine. Manually deleted partitions etc on HDD, made it one big partition for backintime and timeshift to use. All is good.

Now, when booting the laptop, it will start (I can hear the HDD spin up, and I see the screen come on, but nothing displays) then the laptop switches off, and immediately comes on again as above. This happens three times, on the fourth reboot the system starts normally. I have tried changing every single setting in the BIOS, no difference. I do not know much about grub, it seems OK to me, but the problem is probably there.

Please, does anybody know what I can do to fix this?

Thanks!

Some info below:

There is a lot of stuff in /boot/grub/grub.cfg, let me know if I should post it.

johann@sny:~$ grep -v '#' /etc/fstab
UUID=53b002cd-053a-43fe-9e73-9db8c9d545cf /               ext4    errors=remount-ro 0       1
UUID=9A55-24AD  /boot/efi       vfat    umask=0077      0       1
/swapfile

Drives:
  Local Storage: total: 1.82 TiB used: 379.35 GiB (20.4%)
  ID-1: /dev/nvme0n1 vendor: Samsung model: SSD 980 1TB size: 931.51 GiB
    speed: 31.6 Gb/s lanes: 4 tech: SSD serial:  fw-rev: 2B4QFXO7
    temp: 35.9 C scheme: GPT
  ID-2: /dev/sda vendor: Toshiba model: MQ04ABF100 size: 931.51 GiB
    speed: 6.0 Gb/s tech: HDD rpm: 5400 serial:  fw-rev: 0E scheme: GPT
Partition:
  ID-1: / size: 915.32 GiB used: 182.67 GiB (20.0%) fs: ext4
    dev: /dev/nvme0n1p2
  ID-2: /boot/efi size: 511 MiB used: 6.1 MiB (1.2%) fs: vfat
    dev: /dev/nvme0n1p1
Swap:
  ID-1: swap-1 type: file size: 2 GiB used: 0 KiB (0.0%) priority: -2
    file: /swapfile