Steve sleeps mostly on his back, sometimes though he ends up sleeping on his stomach. He doesn’t toss and turn that much, though he does; however, hog the bed sometimes with sprawled limbs.
If Steve was born a woman, instead of a man, she would have been known as Stephanie Rogers and would have tried just as desperately to get a position in the war effort - preferably somewhere overseas - as her male counterpart. Anywhere - nurse, cooking, cleaning, something - but she was deemed to be too small, to sickly. Many people dismissed her; saying she looked as if she could faint at a moment’s notice.
Eventually, she managed to catch the attention of Abraham Erskine and she became his personal assistant. He saw the fighting spirit within the young woman and offered Stephanie the chance to be his first test subject. He knew that if he could change Stephanie into the strong, healthy woman who’s body could match the lion-heart he already saw she possessed that he could convince the SSR that his serum was a success. (Even if many were not happy that Erskine’s first test subject was a woman - they thought it would be better to test a man/”How could you put a young woman in danger like this?”-ness)
The serum was a success; though the moment of celebration was short lived when Erskine was murdered by a HYDRA spy and the serum was lost. Steph became the first Super Soldier and the SSR was at a lost at what to do with their now super-woman. (Many of the higher ups were not comfortable with a woman not looking like Steph did: Strong, solid..)
Eventually they put Steph as the figure-head for War-Bonds sales and to encourage women to join the war-effort: They called her the Lioness of the US. It wasn’t until a tour in Europe to bolster moral that she found a chance to become more than a showgirl when she ran off to save a group of POWs from HYDRA. After that - hiding the fact that she was a woman - she was given the rank of Captain, a team, and sent on secret missions. It wasn’t until after her apparent death that records that ‘he’ was really a she came to the surface. (And even to modern day, many people argue that ‘Captain America was a man!”)
☄ : Any AU headcanon (modern, school, medieval, and so on)
Fantasy Creature AU: Steve would be a centaur - His base would be a type of draft horse (probably Irish Cob), with either a blond chestnut or palomino coloring.
ϡ : mental state headcanon
Steve is moderately healthy minded; though as the years pass by, he grows more tired. The serum keeps his body and mind at top peek, but it does nothing for the memories and experiences he goes through. He has seen a lot and definitely suffers PTSD in varying degrees that shape how he does something. Things he wouldn't have thought he’d do five years ago he might find himself doing.
Betrayals seem to hang heavy on his mind for a while though.
ღ : love or sexuality headcanon
I’ve said it before, but Steve loves to be under his lover. He loves to be able to look up at them, watching their face, to touch their face and hair. Touch and tease their chest, to eventually settle his hands on their hips before letting them wander again.
Steve gets grumpy when his fellow avengers leave their various messes or personal items laying about public areas of the tower/mansion. It’s messy, it means someone else has to pick it up if they want it taken care of right then and there - (and he doesn't like making things harder for Jarvis than needed), and it’s a trip hazard if the messages happen to be in the middle of walk-paths.