SuGoiSuす語彙すGrammar › N3 · 04 Reasons and causes
〜せいか: maybe because; perhaps due to
N3 · 04 Reasons and causes
Guesses at a reason for something, without being sure.
Plain form or noun + の + せいか. The cause is a guess, and the result is usually a mild bad one. おかげか is the good-result version. It is followed by a fact in the same sentence.
Examples
疲れているせいか、朝から頭が痛い。
Maybe because I am tired, I have had a headache since morning.
最近運動していないせいか、体が重い。
Perhaps because I have not exercised lately, my body feels heavy.