Idiom/phrase for acting surprisingly passive [duplicate]

What would you call a person that just stands by and won't act? Is kind of acting like a spectator when in reality that person should do something?

I know there is a word for this because I knew what it was a few hours ago but now I can’t remember it.

Solution 1:

Perhaps you’re thinking of the bystander effect. You could describe someone who doesn’t meet their responsibilities as negligent (failing to act), impotent (unable to act effectively), or oblivious (not even noticing the responsibility to act).

Solution 2:

The word apathy, and its adjective form apathetic are frequently used to describe situations where observers of an event lack the motivation to be involved.

Torpid is a more passive situation of lacking the ability to act, not by its own volition. Whereas, apathy implies an active choice to stay in a demotivated state and inaction.

ap·a·thet·ic (p-thtk) also ap·a·thet·i·cal (--kl)
adj.

1. Feeling or showing a lack of interest or concern; indifferent.
2. Feeling or showing little or no emotion; unresponsive.

[From apathy, on the model of pathetic.]

apa·theti·cal·ly adv.

The American Heritage® Dictionary of the English Language, Fourth Edition copyright ©2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.

torpid (ˈtɔːpɪd)
adj

1. apathetic, sluggish, or lethargic
2. (Zoology) (of a hibernating animal) dormant; having greatly reduced metabolic activity
3. unable to move or feel

[C17: from Latin torpidus, from torpēre to be numb, motionless]
torˈpidity n ˈtorpidly adv

Collins English Dictionary – Complete and Unabridged © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003