Can anyone clarify what's the problem?

alif228 wrote:

My computer just restarted several times and in the error report, it shows:

<Log report.log>

<*** MCA Error Report ***>

MCA = machine check architecture — hardware or very low-level software or firmware.

You do not paint a very big picture or state what exact Mac this is or what exact macOS you are currently running.

See for your particular Mac if you can run the user Diagnostic...not as definitive as Apple's own AST2 (Apple Service Toolkit) back bench diagnostic, but may kick out an error code.

Use Apple Diagnostics to test your Mac

Use Apple Diagnostics to test your Mac - Apple Support

You can get a good look at your System config. and reveal conflicts or issues, you can download/run this trusted utility https://etrecheck.com Allow the Full Disk Access for best results.

If you need help interpreting the report you can post it here in its entirety in the "Additional Text" box in the editing toolbar below, in your reply.

—reboot

—SafeBoot How to use safe mode on your Mac - Apple Support

—reset the SMC How to reset the SMC of your Mac - Apple Support

—reset NVRAM/PRAM Reset NVRAM or PRAM on your Mac - Apple Support

(get at least two-three rounds of the chimes when holding the NRAM Reset)

In or out of warranty you can get a free over the counter 'Apple Service Diagnostics' test /assessment

Make an appointment for a "hardware issue"

Genius Bar Reservation and Apple Support Options - Apple

Outside the USA

https://locate.apple.com/country

Disconnect all external devices in case one of them is causing a problem. Otherwise, you most likely have some sort of hardware issue with the Mac as mentioned by @leroydouglas which will require having the Mac repaired by Apple or an Authorized Apple Service Provider (AASP).