6P randomly goes black and locks up until put on charge

Bit of a weird one, my 6p on Android N (did this on M as well) sometimes just dies out of nowhere, the entire phone just acts like the battery was removed.

Will only come back on if I plug a power source into it, sometimes it resets the time and date when I boot it back up.

Just happened now and the battery monitor shows this:



Any ideas what might be up with it ?

Running official N on an unlocked 6p UK, device is second hand but originally purchased in March this year

Thanks