Hi,
Some updates from me.
After a clean reinstall of Windows 11, I also reverted back to Windows 10 to see if the problem persisted. And yes, it was still present. I also updated all the drivers and even upgraded BIOS version from Dell's official website. No help.
What is interesting, the restarts have gotten worse over time. When the problem first came, the computer restarted once, maybe twice. Now it sometimes even does it 10 times before it "stabilizes".
Furthermore, I also tried Linux Mint OS – but the problem is still there.
Then I took my computer to the shop where I bought it. They did some analysis on it and first told me that the restarting upon boot and battery not charging have two different causes.
According to them, the restarting was an issue of not installing or upgrading Windows properly.
Battery not charing was caused by an USB C port that has become a bit loose on the motherboard, thus not recognizing the charger.
So they advised me to let them reinstall all the Windows 10 (pro version in my case) from scratch, including the BIOS software etc. And also to change the motherboard (around 400–450 euros).
Well, I argued, that the restarting and the issue of battery not charging are related. I decided NOT to have my motherboard replaced (at least not yet) because both of the issues came at the same time and no matter which of the ports on my computer I use to charge it (I have 3 USB C ports), the problem still exists.
So I only let them do a clean reinstall of Windows, drivers, BIOS etc. They did it and told me that the issue of restarting is gone but the battery not charging issue might still be present since they did not replace the motherboard. And that I will still probably need to change the motherboard at some point since the loose USB C port could short circuit the motherboard completely.
As I got home and turned on the computer it welcomed me with approximately 10 restarts. Turns out that the guys at the computer shop had not turned off the computer for at least some 30 minutes to recreate the scenario where the problem returns. They turned the computer on once, reinstalled everything and told that the computer was okay. Unfortunately they did not follow what I had told them.
Then I tried to start the computer (After it had been turned off for a while) in Windows Safe Mode. And...? It turned on perfectly: no restarts and the battery was charging right from the start.
At this point, I am not sure what is the issue. I will take my computer to another computer shop to get another expert opinion what might be causing my issues.
I will let you know if I have any further updates.