Precision 5550 - Crash at startup (on Dell logo)

For the past few days, I've been experiencing an issue with my Dell Precision 5550. I sometimes get a complete freeze in Windows 11, which I didn't have before, forcing me to force shutdown the PC.

Okay, this could be related to a Windows program.

However, when I restart, I regularly experience the problem where the PC turns on, I see the Dell logo, but nothing happens afterward. I notice that the keyboard remains lit (Caps Lock ON), then, without seeing the "spin" icon, it shuts down and restarts by itself.

I sometimes manage to get out of it, I don't really know how, after rebooting repeatedly.

I tried reverting to the previous BIOS using the Dell tool provided for this purpose in the BIOS (by pressing Ctrl+Del then asking to revert to the previous BIOS), and I ran the system tests in the BIOS, which tell me everything is fine except the battery, which is nearing the end of its life (but still working by the way)

Any ideas what could be causing this?

Precision 5550 - (Service Tag Removed by DellAdmin-TOS Violation)