Since the summer is supposedly here (!) here’s an idea.
When too warm in bed, it feels wonderful to flap the bedclothes. Couldn’t a small fan do that? Perhaps. But a motorised arm could.
Why not leave the bedclothes off? That won’t let a single small arm on a motor silently cool you in bed.
A window winder mechanism should be ideal. Just make sure it has something to shield the scissor action mechanism from toes or kids fingers.
Hook that to a random timer or even a thermocouple. Sorted.