I'm in the same situation and I understood a bunch of things. First of all, you'll stutter a lot in front of certain people, who generally have a lot of authority like your boss for example or people who seems very confident and have a lot of charisma. And I really believe this type of stuttering is all about timings, breathing timing, when, where etc.. sometimes you won't block at all just because the timing was perfect. But you'll block some other times because the first word was some " Can I ..." And it won't come out. What I'm saying is.. concentrate on the timings and try to figure out what words are working with you to start your sentence without blocking. Good Luck man were in this together