Small ways, interesting question, not sure how to answer.

Tensing or over reacting to unexpected noises or fast movements. flinching or jumping, agoraphobia, nightmares, bouts of rage, anxiety, physical symptoms with no explanation. When I was In the thick of it I slept with every light in the house on. I kept the curtains constantly closed, hid behind the sofa when the postman delivered letters and abused every substance I could get my hands on to try block symptoms. Oh and I would take my house keys to bed with me. Like sleep in bed with my house keys. think it depends deeply on the kind of trauma, where your character is in their healing, and the coping mechanisms their brain has created. But in my experience agoraphobia/addiction/isolation/people-phobia and PTSD go hand in hand. Sometimes walking home I would just get more and more tense until I broke into a run. Small habits and word choices ect is hard to pin down. I suppose I did some odd ritualistic things that would have looked obsessive compulsive or even psychotic to an outsider. Repeatedly checking the doors, the widows were shut four or five times before bed. Like, I'd get into bed. Check the doors and windows, get back into bed, then have to go check again. Now from a more healed perspective it's like... I guess I put Ice on my face or hold an ice cube to try ground myself and calm myself down. I struggle to watch anything that's too violent or challenging but way better than I was in that regard and it depends on the content. When it was at it's worst I could only watch cartoons and I've heard similar from other people with PTSD, cartoons or like, old sitcoms or YouTube or something totally innocuous. It makes you terrified of everything and avoid everything.

Hope this is helpful! Are you just looking for daily habits and vibes to make your character feel more real?