Black screen interruptions with Apple logo on macOS Tahoe 26.0.1

I run macOS Tahoe 26.0.1. An excellent version as long as it lasts. About every three weeks the screen goes black with an Apple Logo in the center. Immediate restarting doesn't help. I have to wait at least a couple of hours.

Why this? Is it because my iMac 27" of 2020 is about to 'die'?

[Re-Titled by Moderator]

Original Title: Black Screen interruptions