Hello, my brother prebuilt pc sometimes restartes when there are network issues with our internet over the phone line.

Over the summer when the network work's with no issies he never experiences restarts, but the moment we started getting snow and networks issues his pc restarts on random, we know that network issues happen because the iptv box from our carries alwo experience network issue at the same time.

We tried reinstalling windows, also installed bazzite which worked fine, byt yesterday at the same that the iptv box experienced network issues the pc rebooted.

Is there any way to diagnose this and fix?

Edit: this happened when he bought it with a tp link wifi usb dongle last year AND over ethernet since last few weeks.