You can do it, but, it can take a lot of effort, and hopefully the right situation with decent resources.
Leaf litter is usually damp, but, if you sew a big sack from fabric that weighs very little, like ripstop nylon, then that'll pack small and stuff in a pocket, but you can fill it with leaves, straw, whatever and it'll keep it all together to make a paliasse for sleeping upon.....keeps the bugs off you too
Warm, comfortable ?? I think that's a personal opinion. Stuff really, really, really well though if you're trying it.
Ripstop nylon will dry off quickly next morning though.
Folks cut heather and piled it up, bundled together and threw a blanket(s) over the top of everyone. Highland armies didn't carry tents until they became regiments. Sleeping outdoors was normal. Transhumance was a commonplace annual movement of people and animals, the sheilings we find up on the hills were mostly used for dairy produce, storage of stuff. The younger folks bedded down outdoors.
A heather bed is very comfortable, it's springy and keeps the body off the ground.
It's quite a modern thing this sleeping alone. Bundling was commonplace. It kept everyone warm.
If you are sleeping outdoors under your cloak as you suggest though, you might be better becoming accustomed to broken sleep.
Apparently our normal sleep cycle is an hour and a half, and we multiply those up through the night. So, if you sleep for three cycles, get up and move around, have a look at the world kind of thing
and then curl up and go back to sleep again for another couple of cycles, you'll be fine. You get used to it, and you'll not get frostbite
I've slept on fine shingle, which is surprisingly comfortable, with just a bit of oilskin beneath me and a plaid over the top. You need to scoop out a bit for hips and shoulders though, tuck your feet up close. I was young then though, I wouldn't do it out of dire need now.
Leylandii branches (stick the resinous end down into the ground) makes a comfy base too. Smells good.
You'll find links to the hot stones from the fire buried under soil beneath you.
In our climate you can just end up stewing and steaming as if in a sauna
Leaves you and your clothes sodden wet and you shivering later.
Must be brilliant in a cold desert night though
To be honest, I think you might be better waiting a bit and trying all this in warmer, dryer weather. Right now it's just above freezing, and sodden wet in my bit of the world.....and the days are very short too. That means the nights are verrry long. Too long to want to hang around when you can't sleep for fourteen or fifteen hours.
M