The phrase 「どことなく」 (何処と無く) is translated in dictionaries as "somehow", "for some reason", or "vaguely". It seems to be the combination of どこ ("which place?") + と + なく (adverb form of ない).
Problem: I'm trying to understand how these three words combine to mean this (to help me better remember it, and hopefully also to understand it and similar phrases more deeply). In particular: which sense of と is being used to define this word (the quotative particle, the "and" particle, the particle meaning "with"?)?
My best guess is "some place and notly" (here "notly" is my attempt to turn English word "not" into an adverb to fit ない being a 副詞).