Luffy talks in his sleep
Rarely a minute passes by in the night without a muttered 'meeeat' or 'adventure'. Often he says names. Often theirs, sometimes others'. Sometimes they are ones they recognize, sometimes not. Sometimes they are obviously merely placeholders for names he never bothered to remember, but though the names escape him, he always remembers the people.
He moves too. Trashes around in his sleep like a hyperactive child on itching-powder, arms and legs sprawled all over beds and nearby people. He rarely stays on top of the pillow and under the covers. More than once, he has fallen off the bed or hammock and just kept sleeping. Falls from that height hurts him less than a literal feather-touch.
Though, sometimes, sometimes he sleeps quietly.
Some nights, the only sounds to escape him are nearly inaudible whimpers, only sounds at all if they listen hard. Sometimes the constant snoring and muttering stops. Sometimes, his limbs are not sprawled as far over the edge as possible, trying to escape, but are pulled up close. Sometimes, he pulls his knees closer to his body and curls his arms tightly, desperately around his chest.
Zoro is always the first one to notice, woken by the unnatural silence as he always wakes to danger, and the rest of the boys are soon roused by the sound of his swords moving with his rapid steps as he crosses the floor and tries to shake his captain awake. When he finally wakes up, Luffy grabs on to Zoro's hand with a grip so strong even the swordsman would have trouble breaking it, and says his name in a smaller voice than they have ever heard in daytime, as if he is both asking if Zoro is there and begging him not to leave. Someone, anyone, will answer 'it's alright, we're here, everyone's here, everyone's alright' and he looks at each of them in turn and says their names, just to reassure himself.
One of them runs off to fetch the girls and whoever is on watch. On every other night, a man walking into the girl's room would be incapable of walking out by his own power, but when one of them bursts into the room with a simple 'Luffy needs you' they both simply get up and walk to the men's bedroom. And then they are all there, and they are touching him. Touching his arms, his hair, his shoulders, chest, back, side or legs, just to make sure he knows they are all there, are all unharmed, and soon he breathes again and it feels like their first real breath since they went to sleep.
After, they all go up to the galley, no one feeling like going back to their own beds. Sanji makes snacks, heats leftovers and makes hot chocolate, and they sit and eat and chat and laugh and sing, and soon they are all passed out on the galley floor. Luffy thrashes around and makes noises and annoys everyone, and they wish he would just stop being such an impossibly restless sleeper.
Sometimes he sleeps quietly.
They are trying very hard to make him stop.