Vivobook shuts down shortly after boot - even in BIOS

[Robocop]

Hi everyone,

I'm trying to figure out what's causing my laptop to boot up, but then shut down after about 30 seconds. It does the same thing whether I'm in BIOS or booting into Windows.
Here are the specs:

• Model: ASUS Vivobook Go 15 (E1504GA-BS31-CB)
• CPU: Intel Core i3-N305 1.8 GHz
• RAM: 8GB DDR4 (onboard)
• Storage: 256GB M.2 NVMe SSD
• Motherboard: E1404GA_MB REV:2.1 E89382 MV04 HSB J 2426 94V-0

The laptop was working fine earlier. The user closed the lid to put it to sleep (as they always do), and when they tried to use it again a few hours later, it started shutting down after about 30 seconds.

So far, I've:

• Replaced the thermal paste
• Disconnected the internal keyboard
• Removed the battery and booted with just the power brick
• Tried a different power brick
• Ran the fan test in BIOS — the fan was spinning normally

But the issue still persists.
Any ideas on what could be causing this?

Thanks in advance!