Stutter goes away when voice acting?

Stutter goes away when voice acting? like it says on the tin; I have a stutter that is more aggressive when im tense or on the spot, but i run a tabletop roleplay game (3+ years strong now!) and while i have one character that retains my type of stutter, none of the other characters have it. strangely enough, i NEVER get frozen on a word or stutter when doing their voices, despite the fact that i'm doing improv in front of like four or five other people. anyone else experience this?