This happened to us last year, cabinets in the kitchen banging open around 3-4am a few nights running. My partner was convinced it was just the wood expanding or something but it happened in summer so I'm not sure that explanation holds up really.
Did yours slam open completely or just kind of creak open? Ours were fully open each time which is what got me, like they'd been pushed. Nothing was ever disturbed inside though which I found strange.
Has anyone ruled out the obvious stuff like vibrations from traffic or a boiler kicking in? I'm trying to be methodical about it before jumping to conclusions but part of me does wonder. Would be good to know if others have had the same thing and what you made of it.