I don’t think specific languages affect stuttering, but if someone is bilingual they may stutter more in their weaker language, the one which requires more thought to communicate in. That is certainly the case with me. My primary language is English, and I also speak Spanish (of the Cuban variety which is much softer/more relaxed than European Spanish.) When speaking Spanish I struggle considerably more. I think this is because I need to think about my words more, and I’m simply not as comfortable in general which causes extra stress and hesitation.