Mine is kind of similar. I stutter a lot in social situations when I get excited or happy about something. I start talking faster, my brain outpaces my mouth, and it just falls apart. Like I’ll be talking fine then just get blocked suddenly and look like I’m choking as I fight through it. But like you, I can also stand up and give a speech without missing a beat if I’ve rehearsed. I also don’t really stutter in interviews where everything I’m saying is deliberate and slower.