(of a person) not able or willing to show feelings or take part (because nervous, arrogant etc)

remote

not willing to be with other people

nonparticipating; avoiding company

showing that one is inferior, less able etc

meek, unassuming

(of a person, character) slow to express feelings or opinions; (of a seat in a train, room in a hotel etc) kept for a person's later use

silent, unsociable; constrained

without companion; (preferring to be) alone; single; seldom visited

alone, single; unsociable

(especially of a person) difficult to talk to (because too formal)

unfriendly

not communicative

shy, silent

not showing one's true affection, interest etc

cool

not willing to be with others

unfriendly

(of a person) unusually quiet and shy

unsociable