Apple Watch Series 10 speaks current time randomly

I have an Apple Watch Series 10, which I wear overnight as recommended.

Occasionally, without any prompting from me, it announces the current time (e.g., '10:49').

Funnily enough, it doesn’t add 'It’s' beforehand as it does when I ask for the time (e.g., 'It’s 10:49').

Either way, it shouldn’t announce the time at all! It often happens in the middle of the night and wakes me up!

Any idea why this might be happening?