Xbox One switches off during gameplay

For the past few months my Xbox One has started crashing during gameplay.

It performs perfectly whilst playing DVDs or watching shows on streaming apps, the crashes only occur when games are playing.

It seems to happen with every game I play, it is not just one title.

Sometimes the game would freeze, a loud buzzing noise would sound and then the game would crash and I would return the Home Screen.

Mostly, the entire console just switches off.

This is happening with both disc-based games and digital versions.

So far, I have tried:

• cleaning the vents and removing dust from the fan.
• extracting the HDD to look for any corruption (although Im not confident on this sort of thing).

Not sure if this might be related to the power supply as it has been plugged into an extension cord for the past few months, but I don’t get why it would happen on games but not other things unless it’s just because games require much more power?

Any help gratefully appreciated.

Thanks, Adam