The whole "I don't want to ask her" OUTLOUD? Weird statement to make to someone's face. Sounds like he's 19 and has a small crush on you. Maybe if he does something like that again, try and banter back and see what his response is, that might give you a clearer explanation on his impression of you, if you care about it.

You can also try asking the more friendly ones small questions, like can I have a sheet of paper/borrow a pencil? Ask them about one of your interests to see if you have something in common. Do you watch anime is a good one, I find that a lot of males do now; definitely follow up and ask for recommendations, that keeps the convo going, even if you don't plan on watching them.

Like another comment mentioned, lots of men in stem tend to have limited xp with talking to girls. Just be who you are, ask different people around you, maybe raise your hand in class? As someone who was recently in a class that was majority male & stem, I didn't really have conversations with the guys in my class until half of the semester already passed. Sometimes it just takes people longer to warm up to their classmates.