Hi Marc
We had the same situation with our last foster but it only seemed to be if someone passed the house or woke her. It became a tiny bit worrying as our neighbours had small kids and early starts…Not sure what it is, probably changing the bed is the best thing. We moved our little fellow into the front room that’s sealed off in he back of the house and that seemed to work..Don’t worry about the utilty being that cold- you’d be surprised how resilient the pooches can be..Sorry, I can’t be more help..Think it’s just part of the process..Best of luck
M