The noun reticence means an unwillingness to do something or talk about something.

Synonyms are hesitation, shyness, closeness, or reserve.

The word origins from Middle French (16th century) réticence and Latin reticentia meaning “silence, a keeping silent”, from the present participle stem of reticere meaning “keep silent”. It comes from re- plus tacere  meaning “be silent”.

She observed in public a constitutional reticence on the subject.

Despite his reticence, it is impossible to doubt that he was fine.

The old man paused until his anger overcame his reticence.