Yea I think it's quite common to stutter more in non-native languages. In my French class I find it very hard to participate verbally. And it makes sense thats it's more difficult. Not only are you unfamiliar with certain new sounds in a language but you also have that mental load of translating in your head from native lang to secondary lang. So you'd be thinking of things like sentence structure, what vocab to use, correct pronounciation etc.. All the while having to focus on you're speech and worrying about whether or not you'll be able to say that word or sound. So a lot of emotional and cognitive stuff going on.