Thanks a lot Mart for your suggestion. Yes, I was using NVIDIA prime in hybrid mode.
I have been trying different things now and also had lost the ability to run the NVIDIA driver in Hybrid mode.
Setting GRUB_CMDLINE_LINUX_DEFAULT ="quiet splash acpi=off " in /etc/default/grub made it work again , which might suggest that it is a power issue with the 4k OLED display . Note that connecting a HDMI display always works.
Then I downgraded and upgraded the BIOS and now at least I got the NVIDIA 470 driver work in Hybrid mode - without acpi=off. So maybe there were some corrupted settings in the BIOS?
I think I am going to work in hybrid mode using NVIDIA prime .