[enyafriend]

何だか[なんだか][nandaka]=somehow, when you're unsure of something

e.g.
なんだか吐き気がします
Nandaka hakike ga shimasu
I feel like thowing up

何がなんだか分らない
Nani ga nandaka wakaranai
I didn't know what was that

何だかすごく疲れたね
Nandaka sugoku tsukareta ne
Somehow I felt really tired

"Nandaka" is a very common expression and is taught when in either level 3 or level 2 standard.