Hello. I think a cleanout can make them a bit stressy and hide away more. Not sure how you do this, but general advice is to only do "partial" cleanouts. Eg if you do the substrate then leave everything else until another time - wheel one week, any toys another week. I also leave the nest alone and in tact unless pee'd in and the same with the hoard - although may "prune" the hoard if it is getting large - I take the bottom half out as that is the oldest food. If you ever do need to remove the hoard, eg if it is pee'd on - always replace it with new food in exactly the same place or they can start peeing on it to deter thieves! Then it's a catch 22.
Even when changing the substrate, I save about a third of the old substrate that is clean and spread it on top of the new. This way something always smells familiar in their cage and they get less stressed about cleanout and avoids them having abnormal behaviours.
If the substrate is deep enough - eg 4 to 6" - then you can "spot clean" mostly - ie take out the odd handful and replace it now and then - and then you can go much longer before having to do a substrate change. I use a litter tray and empty that every few days, spot clean and only need to do the substrate every 8 weeks or longer!
Anyway the other reason for a change (and it may well be a bit of both) is it is starting to come colder. Hamsters start building bigger nests and keeping warm and cosy as soon as they feel the cooler change in the air. They really do feel the cold - to the point that if they get too cold they can go into "torpor" which people call hibernation but it is not a good thing. They rarely survive coming out of torpor.
Ideally the room needs to be between 16 and 20 degrees fairly constantly. In winter with freezing nights, I use a little oil filled radiator on a timer overnight for 2 or 3 hours to prevent the room getting too cold over night (rather than have all the central heating on in the night which is unnecessary).
If you have just cleaned the wheel this may be why he isn't using it
Our first syrian wouldn't go near his wheel if it had just been cleaned (stranger! Wheel smells different!) and I used to have to tempt him back in by putting a smelly treat in it - eg a tiny bit of cheese or cucumber, then he'd start using it again. You could try that.
It's a time to make sure there is plenty of nesting material put out regularly - a pile of torn up strips of plain white toilet paper - they take it to make their nest cosier. As it goes down, keep adding more every few days.
Also is his house big enough to build a big nest in?
Conversely when the room is warm and cosy with the heating on, they often start coming out more and wanting more out of cage time.