I commiserate with your situation Calgacus03. I wonder if your bed was copping a random vibration from nearby machinery travelling thru some sort of rock substrate under a foundation stump beneath your bed? Did it ever happen again? It sounds like a recipe for desertion anxiety.
Sorry AlchoPwn, I've only just come across your reply to my post.
No, there was/is no type of subterranean travelling (or tunnelling) in that part of the world (a small north-east coastal town) and the house in question was a four-square, sandstone built, detached affair, probably dating from about 1870 or so. So no foundation stumps (I shouldn't think).
There was coal mining at one time in the area, but that was several miles away on the other side of the river, and stopped during WWII.
I've tried to think of a rational explanation for it over the years, but have come up empty. It never happened again, and I continued to sleep in that bed and bedroom until I was about twelve or thirteen (by which point I'd
pretty much outgrown the bed), I then got a proper bed in another room at the back of the house.
I haven't asked my cousin whether he remembers it, once lockdown is over and I see him, I'll see if he does and whether he'll be amenable to providing his recollection of that night. He normally has a pretty good memory for events from our childhood.
As for "desertion anxiety"

no, I don't think it led to that. As I recall (and it was
many years ago) during most of the occurrence I was frustrated (by M. denying that he was doing it when I
knew that he must be (because
I wasn't)). Puzzlement (when I realised that neither he nor I were doing it), and only fright (when M. bolted) and I realised I was on my own.
