If this is a first time experience taking an amphetamine
such as Vynanse, it's quite possible that your behavior will be noticeably different. One very common trait is being unusually talkative. Your mind/intellect is likely to be very active, (hopefully) very sharp and thoughts & ideas, etc. will come to you much faster than usual:l that's one of the reasons it's great for studying, writing and anything that requires sustained attention and energy. But all of that, combined with the mood elevation and physical energy frequently results in very fast or even breathless speech. Of course if you're normally a very energetic, engaged, fast thinker and talker, then these behaviors might not stand out that much but if that's not the case, you'll have to make a very strong effort to keep your affect normal, and um, your mouth shut, LOL!
Other things that could draw attention: making it obvious that you have a very dry mouth, smacking your lips, etc. It's also very easy to slip into small, very repetitive ticks or tweaks that to you just feel like fun little ways to express or let off some of that extra energy. A major attention getter is grinding or clicking your teeth, though that usually appears with higher doses and prolonged use, though sometimes that shows up more when you're starting to come down. While that kind of thing might provoke a joke from your mates about how badly you're tweaking, you're likely to be staring at knitted brows and a some relentless interrogation if your parents pick up on it. Oh, yeah, might be suspicious if you don't eat for a day or too, so learn to make yourself eat!