what does the knight propose to the knights and why don't any knights respond initially?

The Knight xplains that he has come to this famously valiant court to play a Christmas game. Whoever agrees to play this game will be allowed to strike the Green Knight on the spot, in the middle of the court; in exchange, the Green Knight will strike a return blow upon the volunteer a year and a day hence. None of the court volunteers as the game seems to imply certain death for whomever plays; the stranger ridicules them all for Camelot's supposed bravery. Eventually Arthur agrees to play the game, but as he is about to wield the great battle-axe, Gawain speaks. In polite and self-effacing language, Gawain begs to take up the boon instead, so the life of the king can be spared in place of a knight as weak and lowly as he. Really a knight should have stepped in before but at least Gawain was better late than never.