Clicking Apartment Door Lock

My apartment door makes a strange clicking noise at various intervals throughout the night(presumably during the day too but haven't noticed). I've tried locking and unlocking it in various ways before bed but with no luck and almost every morning between 7 and 8 there's a big noise out of it like it's just clicked in or out of place. I know this is wierd but it's just annoying and wondering if anyone could shed light on it.

I used to hear a similar sound but turned out it was the timer in the hotpress going from the night time setting to the daytiime setting.

And if it's not the hotpress, we getthe same noise from our electric box as the night saver time kicks on and off, does sound like a loud light switch so it could be that also.

That makes sense as both hotpress and electric box are next to door. Thanks for replies.