CHOCK IT!!!
If your vehicle is unhooked, you MUST CHOCK your camper!!!
Would you park your vehicle and leave it in neutral without a parking brake, just hoping it wouldn't roll away? And then bounce around in it for a few days, hoping the same thing?
Danger, danger, danger! I cannot stress that point enough.
Now, it is also important to chock BOTH sides of the trailer so it does not pivot on the free-rolling axles (that is what they are designed to do, roll without resistance).
When unhooking, chock both sides first, leave the safety cables/chains connected and jack up the tongue and unhitch. Keep your feet out from under it and watch your pinch points. After it is unhitched and has not moved, you can remove your safety cables and such.
Please heed this advice. Getting hurt or causing damage over this is unnecessary and so very preventable.