Natasha likes the way Steve almost unconsciously reaches for her when something explodes around them.
She likes the way he'll tuck her body against his, enveloping her almost completely. The way her fingers brush against his pulse as she reaches around his neck, and how he'll duck his head down next to hers.
Crouched against him, she likes the way his solid body muffles the sound of the blast. She can smell smoke and dust and gasoline but for some reason Steve's musk always breaks through, comforting and inviting. He smells of army regulation soap and of something inherently masculine, but at the same time of sweat, grime and fighting and it's not the slightest bit unpleasant.
She likes the way his arms feel around her, holding tight and keeping her still. Keeping her safe. Keeping her so close. She likes the way his shield covers both of them, an impenetrable barrier, but really it feels like Steve is protecting her more than the shield ever could. Like even if he didn't have the shield he would still throw himself around her without hesitation.
One thing she definitely doesn't like though, is how quickly the moment fades. The threat passes and he's already moving, drawing away from her. Already fighting. Moving boulders bigger than himself. Doing whatever it is he needs to be doing to make sure everyone else is safe too. She doesn't like the way in which his presence slips from her like smoke, but she carries on regardless because he's counting on her to have his back. He trusts her and she can't let him down.
And Nat can't help it if she's mentally looking forward to the next time he'll pull her into his arms.
Not that she would ever tell him any of this.
Steve just wishes it didn't take an explosion or collapsing building to get so close to her.