Explanation
Used to express 'without a particular intention', 'unconsciously', or 'before one knows it'.
Formation
Verb-dictionary form + ともなく + Verb
Detailed explanation
The phrase VerbるともなくVerb indicates doing something unintentionally or unconsciously— you just find yourself doing it without a clear aim or intention.
Examples
Tooku o miru tomonaku mado no soto o nagameta.
I found myself gazing out the window, not really looking at anything in particular.
Shiru tomonaku, kare ga satta koto o kanjita.
Without really knowing, I felt that he had left.
Hon o yomu tomonaku, peiji o mekutte ita.
Without intending to read, I was just flipping through the pages of the book.
Neru tomonaku, beddo ni yoko ni natte ita.
I was lying in bed without really intending to sleep.
Practice
Grammar content sourced from hanabira.org.