Your statement as written isn’t entirely clear. Does your ‘I don’t know why ‘ apply to all the languages, or just English? Also, it isn’t grammatically correct. I don’t know why, but I’m in the mood to study French and German, but not English. I’m eager to work on French and German, but for some reason I’m not in the mood to study English. (This implies that it is obvious or expected that you are motivated in French and German) In general when you say that you don’t understand your own motivations, you’re implying that they’re important. Maybe you’ll speculate about them.

I don't feel like studying English.

'I'm excited to study French and German but not so much English right now."