What is wrong with my bird?

I’ve never seen a chicken do this in my life… I got a new batch of little ones and I think this is a roster (not 100% sure yet). He is the smallest of 3 potential rosters (the other two im pretty confident are rosters). Yesterday I noticed him doing a strange thing with his neck, his eyes were closed and he was alone(the new gang hang pretty tight). My first thought is he lost a fight and has a broken neck… I checked on him multiple times and he didn’t improve… I figured I’d get the chopping block ready, it’s quick cold in my area and dying slowly in this cold didn’t seem fun. But this morning I went to go get him and he was doing his same old weird neck thing, so I gave him a little poke and up he popped, he wondered over to go eat some food and although his neck was still on an angle he was pecking at food no issue… so I let him be. But still have no clue what’s up with him.