Bucky is out cold when Steve climbs up into the truck again to check on him. Snoring, fortunately, so he's actually asleep this time, not just unconscious.
He starts to stand, preparing to leave, but a choked noise, low in his friend's throat, stops him. Bucky mutters plaintively once or twice, and yelps in his sleep before rolling over and hunching into a ball. He shivers hard then goes utterly still, but for the faint rise and fall of his shoulders as he breathes. The choking noise comes again, muffled, like he's trying to stay silent.
Steve almost moves to wake him, but stops himself just before his fingers make contact.
If Bucky balked at a friendly hand when he was awake, he'd probably come completely unglued if someone woke him straight out of a nightmare. Steve hesitates a moment, then contents himself with squeezing into the tiny space at Bucky's back, to share whatever of the warmth he now generates like a furnace that he can, and tries to get some sleep himself.
It's all he can give for tonight.