Why does the roommate in the upper bunk keep shaking?

Roommate's bed is always wobbling, there may be several reasons. First, when a roommate listens to hi songs, his body will shake unconsciously when he is conquered by dynamic and rhythmic music.

The second is personal habits. Many people have the bad habit of shaking their legs, which is caused by unconscious instinct. They won't notice that they will feel uncomfortable if they don't shake their legs, so shaking their legs will cause the bed to shake.