。
Could you make a reservation for me?
Literal
Reservation do-[benefactive-potential-てもらえますか]?
~てもらえますか is the polite potential of ~てもらう ('to have someone do X for me, to receive the favor of X') — literally 'can I receive the doing of X?' A softer alternative to ~てください because it frames the request as asking whether the listener is able to help.