For now should I have lain still and been quiet. "In that case, I should now ( עתָּה) have been lying still and resting myself," instead of tossing about, and being full of restlessness and suffering."
I should have slept. The life in the intermediate state is called "sleep," even in the New Testament (Matthew 9:24; John 11:11; Acts 7:60; 1 Corinthians 15:18, 1 Corinthians 15:51, etc.). Job, perhaps, imagined it to be, actually, a sound, dreamless slumber.
Then should I have been at rest; literally, then ( אז) would there have been rest for me."