When we winter camp we do this:
When doing any cooking or dishes, crack a window near the stove open.
When showering, open the vent a good 1 to 2" to vent moisture out.
When sleeping, crack open a roof vent a good 1" to 2" inches. We do the one the farthest from the bed room.
During the day, leave the vent open as well, just may be able to close a little.
We use a dehumidifier
We do the shrink wrap on the windows.
Get a humidity meter to measure how good or bad it is.
If you are doing winter or cold weather camping in your 2 or 3 season camper you have to deal with moisture and keep it in check or it can over time start problems.
Small spaces, Single pane glass, aluminum window frames, no vapor barrier, no attic vents in the roof all add to the problem. While you cannot practically redo the way your camper is built, you can understand the moisture problem and compensate for them. Cool/cold weather camping can be fun. No bugs, fewer people, nice and peaceful.
Hope this helps
Good luck
John