MacBook Pro 14' (2021) restarts when closing the lid

My MacBook has been restarting by itself when its lid gets closed, for a while now. It has been quite frustrating and I'd decided to look into it, but still can't figure out the reason.

The issue persists both when laptop runs on battery and when it's plugged into power adapter.

As far as I could tell, when MBP is plugged in, it keeps on restarting every 20-21 minutes until i plug the cable off, providing this annoying macOS startup sound. If it runs on battery, it only reboots once the moment lid gets opened.

When the system restarts, no panic message is being shown, the only thing reminiscent of something wrong happening are the ResetCounter-<timestamp>.diag files, which all look like so:

{"os_version":"macOS 14.4.1 (23E224)","bug_type":"115","timestamp":"2024-04-28 09:58:46.00 +0300","name":"Reset count","roots_installed":0,"incident_id":"9105F79D-8680-4D74-9392-59CE341538CD"}
Incident Identifier: 9105F79D-8680-4D74-9392-59CE341538CD
CrashReporter Key:   55612C6E-A267-19AE-ED57-A080DCB76B45
Date: 2024-04-28 09:58:46.43 +0300
Reset count: 0
Boot failure count: 1
Boot faults: btn_shdn,btn_shutdown
Boot stage: 0x50
Boot app: 0
socId: 6000
socRevision: 21

Boot fault on btn_shutdown seems dubious, and I couldn't really find any information online about what this even is supposed to mean...

I've tried:

1) Booting into safe mode

2) Changing hibernatemode to 0 in pmset

3) Running Apple Hardware Test (resulted in "There may be an issue with System Management Controller", Ref. code: IMU001)

4) Repairing disk

5) Updating MacOS to latest release (14.4.1)

None of the above helped with the matter. The only thing that leaves some sort of clue to what's happening is the Hardware Test result, but AFAIK IMU001 is an error related to accelerometer/gyroscope, which frankly seems almost unrelated to the case, and I couldn't find any similar issues online.

What could be causing such a weird behaviour? Haven't ever encountered any problems related to my MBP, but this one seems persistent and is honestly quite frustrating.