"without rhyme or reason" in Chinese (Simplified)
莫名其妙毫无道理
Definition
“without rhyme or reason” 形容某事没有明显的原因、逻辑或目的，看起来很随意，毫无头绪。
Usage Notes (Chinese (Simplified))
多用于口语，用来表达对无法解释或莫名其妙事情的无奈或困惑。'莫名其妙'是最自然的对应语。
Examples
He started laughing without rhyme or reason.
他突然**莫名其妙**地笑了起来。
The dog barked all night without rhyme or reason.
狗整晚都在**莫名其妙**地叫。
My computer shut down without rhyme or reason yesterday.
我的电脑昨天**莫名其妙**地关机了。
Sometimes, people just leave jobs without rhyme or reason.
有时候，人们就是会**莫名其妙**地辞职。
Her moods change without rhyme or reason these days.
她最近的情绪总是**莫名其妙**地变化。
The plan was canceled last minute without rhyme or reason.
计划最后一刻**莫名其妙**地被取消了。