Adrian Caspersz expressed precisely :
On 05/02/2019 10:54, Harry Bloomfield wrote:

I then decided to pull it apart and try some reseating, but before that
take a look at the Virtual Memory settings - that was on automatic, with
8Gb of actual memory. As a test I took manual control of that and set it to
Min 1.5x, Max 3x the 8Gb. Since when there have been no further lockups.

Sit down with Procmon and work out what process is grabbing that much memory.

Assuming that has fixed it - I thought W10 was supposed to let you know if
it was running out of Virtual Memory, not just freeze or lockup?

That will be logged in Event Viewer I expect.

All it seems to have recorded, is 11x 'The system has rebooted without
cleanly shutting down first. This error could be caused if the system
stopped responding, crashed, or lost power unexpected...' in the past
24 hours..

Nothing else obvious I could see from that..

Memory in use - 46% largest taken by Firefox at 660Mb with a lot of
tabs open.