twiddle one's thumbs

To wait idly because one cannot take action or has nothing to do at the moment. Although the phrase refers to an actual movement of the hand (in which one's fingers are interlaced and each thumb is brought over the other in succession), the phrase is usually used figuratively. I'm just twiddling my thumbs here in the ER, waiting for someone to give me an update on Claire's condition.

Be bored or idle, as in There I sat for three hours, twiddling my thumbs, while he made call after call. This expression alludes to the habit of idly turning one's thumbs about one another during a period of inactivity. [Mid-1800s]

To be bored; to be idle. The habit of idly turning one’s thumbs about each other during a period of enforced inactivity gave rise to this cliché, which began life in the mid-nineteenth century. “You’d have all the world do nothing . . . but twiddle its thumbs,” wrote Douglas Jerrold (Mrs. Caudle’s Curtain Lectures, 1846).