なぜだか

adverb

somehow; for some reason; without knowing why

Expresses that something happens or feels a certain way for an unknown or unclear reason; often used when the speaker is puzzled or cannot explain the cause.

See also: 何故か (なぜか)

• なぜだか今日きょうはとても疲つかれている。

  For some reason I'm really tired today.

• 彼かれはなぜだか急きゅうに怒おこり出だした。

  He suddenly got angry for no apparent reason.