I wouldn't call it stuttering. Since I tend to be more social online, when I talk IRL I try to use bigger words than I'm used to and can't find the right word immediately, so I just pause for a few seconds, then use a smaller word
Since you can think before you hit enter online, I can generally word everything I say better. I guess I got so accustomed to doing that, and it doesn't work IRL.
If I get REALLY into talking about something, or telling a story, I never have that problem.
If that made any sense at all.