Cedric does not like the sudden onslaught of limbs. His head hits the thin wall of the coffin, thumping painfully against the wood. It definitely lifts the fog from his mind. Several key facts are processed:

He's in a small, dark wooden box.

It's a coffin.

And his coffin-mate is attacking him in a desperate attempt to escape.

Cedric should probably help with that. He lifts his arm and leg, whacking upward as hard as he can. No, that's not the right spot. Is his wand here? That would be useful. His hand searches the space, though he yelps when the other occupant hits him.

It's clearly panic. Cedric's mind is admittedly racing too, but he knows from his experience in dungeons that they won't get out this way.

"Hey! Hey." He tries to get the other person's attention.