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

remote

not influenced by personal feelings or interests

detached, uninvolved

not sensitive (to touch, light, to the feelings of other people)

indifferent, callous

(appearing) tired, unenthusiastic

careless, indifferent

taking too little care; guilty of neglect

careless, indifferent

having or showing no interest or enthusiasm

easy-going, laid back

without ability to feel or move (because of something)

deadened, insensitive

not anxious (about); not (emotionally) concerned (with)

carefree; apathetic

not showing one's true affection, interest etc

cool

having, showing, no interest; having no personal concern in something

oblivious to

not quick at noticing things

not observant

(of a person) unusually quiet and shy

unsociable