That seems like a normal restart initiated by using the start menu. The error code 0x80000000 does stand out, since on my personal Windows 10 install a normal restart gives a code of 0x0 (Indicating success). The "Other reason (Planned)" is normal though, it's simply the default reason for the shutdown command. The error code 0x80000000 isn't actually a specific error code that says anything, it's basically the 'empty' error code (Since error codes from windows system calls range from 0x80000000–0xFFFFFFFF). I think it might simply mean the restart was cancelled, which you would know if you did, or maybe if the restart failed for an unknown reason.

Did you confirm the message occurred roughly around the time the unexpected restart occurs? If the timing doesn't align, it might just be a complete red herring.

But if it aligns, something is somehow using your file explorer or task bar (which is what explorer.exe is) to initiate the restart, which would be unexpected since most often it would just directly shut down the computer by issuing the command for a restart directly (And you would see the process that initiated it instead of explorer.exe)

You might be looking at something that injects itself into the windows explorer, or something that directly uses keystrokes or mouse inputs to control the start menu (But you might be able to see that if so). Not necessarily nefarious but you should be on guard anyways. Maybe hotkey or macro software, or software you installed that works through the right click menu in the file explorer, or anything that adds itself on top of the default windows explorer like toolbars or plugins. A virus or such would be possible too, although one would wonder why it would just restart the PC and not actually do anything in secret. In cases where it's not a virus, there would likely be a pattern to where you perform a specific action and the restart occurs.

I would probably run down a classic troubleshooting checklist like remembering if you installed anything recently that aligns with the issue starting to occur, checking if there's any unknown applications starting with windows (You can check this in your Task Manager -> Startup), and running antivirus more aggressively (Such as scanning the entire disk). And if you can, ask around on forums where people much more familiar with this stuff hang out (Like here) or involve someone with more knowledge that can physically access the PC like a local computer repair shop or a tech-savvy friend.