Do you know Sarah my Harry did this just a couple of weeks ago out of the blue.
Harry is in a imac fantasy cage has slept in an open nest in the downstairs corner for months perfectly happy.
And decided to use the tubes as a shashing place(dog bones!!)
and bed with tissues totally the out of the blue.
Has Mzrvin got a wee hidey hole place for himself to hide away if he needs to
I bought hARRY a plastic igloo house and he is now happily sleeping in that.
Hope this is any help to you maybe he needs just A wee bit of time to himself sometimes.best of luck hamsters may e small in body but sure are lagrge in character lol thats why i have 4