One of the nicest things about Cas, to Dean, was that he didn't ask questions. Some nights Dean woke up gasping and covered in sweat. Sometimes the dream would be forgotten as soon as he woke up, but other nights they would stick around. On nights like that Dean slipped out of bed, being very careful not to disturb the angel sprawled out next to him. On nights like that Dean would seek out a distraction.
Usually he ended up watching TV or flipping idly through a book in the library. Just a change of scenery tended to help force his darkest thoughts away. And besides, Dean had found that focusing on getting back to sleep after he woke up from a nightmare just made it harder to actually fall asleep. After a while, be it twenty minutes or an hour, Cas would join him. Dean had never been able to figure out just how the angel ever noticed he was missing. The guy slept like a log. But inevitably, Cas would appear.
He would shuffle, blinking and quietly grumpy, through the bunker until he found Dean. He would be sporting a blanket over his shoulders, usually trailing on the floor behind him. Upon finding the hunter, he wouldn't hesitate to curl up next to him. He would whip the blanket around to cover both of them and lean his head against Dean's shoulder. Then he would search for Dean's hand under the cover and take it in both of his own. Then Cas would close his eyes, but Dean could tell, Dean could always tell, that he wasn't really asleep.
On nights that Dean felt like talking Cas would open his eyes and tilt his head to keep Dean's face in view without lifting his head from Dean's shoulder. On nights when Dean didn't feel like talking Cas would keep his eyes closed and use his thumb to rub circles against Dean's palm. Regardless, Cas never fell asleep until after Dean's eyelids started to droop and the hunter's head fell to rest against the angel's.
Inevitably, Dean woke to sore muscles and a stiff neck from sleeping in a mostly upright position. He always woke up before Cas, because Cas was most definitely not a morning person. The hunter would stay still for a while. He liked sitting with Cas while the angel was asleep. There was something peaceful in it.
Unfortunately, Dean could never hold his position for very long. Cas would wake up to Dean squirming underneath him. The angel would lift his head, blink at his surroundings for a moment, then aim a small smile at Dean before pushing himself to his feet. Dean would stand up as well and stretch the kinks out of his muscles. Dean had learned quite quickly that Cas's tongue turned acidic in the morning. It was best not to speak to him until he was fully awake.
Cas would retrace his steps from the night before, seeking out the comfort of Dean's bed, where he would sprawl across the mattress for another few hours. Dean would head for the kitchen, flick on the coffee maker, and get started on making breakfast. Three or four hours later, Cas would make his first real appearance of the day. Showered, teeth brushed, perennial bedhead still in place, and dressed in jeans and a sweater, the angel would stroll into the kitchen and peck Dean on the cheek before seeking out a sugar laden cup of coffee.
The nightmares of the night before as good as forgotten, Dean would present Cas with a plate of food he'd saved for the angel. Cas would glance him up and down, checking, Dean was sure, to be certain that the hunter was okay. Then the pair of them would sit at the kitchen table, and Dean would nurse a cup of coffee while watching Cas eat. Sometimes they spoke, and sometimes they didn't, but Dean didn't mind it either way, because sometimes the angel's quiet but sturdy presence was all Dean really needed.