On this page, you can learn Japanese onomatopoeia to describe fear, uncertainty and nervousness.
My older brother is very agitated now.
そわそわ describes the state of uncertainty.
ざわざわ describes the state of uncertainty.
I feel cold.
ぞくぞく describes somebody who feels cold. The person is likely to be sick.
ぞく describes the state of fear.
ぞわぞわ describes the state of fear.
There are many ぞs in the manga above as ぞ is the first letter of ぞわぞわ and readers understand he is scared of something from his facial expression.
I am nervous as blocks may collapse.
A girl is angry.
ぷんぷん describes the state of anger. It is used for a girl or someone little or cute. The level of anger is not that high.