Do you typically talk to this person in person? If so, then you should probably go ahead and text him saying "hey" and ask how he is. If he wonders how you got his number, you can tell him that you got his number from a mutual friend and unless this dude is super paranoid or something, most people aren't going to flip out over this especially if you guys already talk to each other when you see each other. I've done this a few times with people I know (regardless of whether I was attracted to them or not) and most of them would respond pretty well to it if I was already on pretty good speaking terms with them in the first place.
However, if you don't really talk to him in person then it's probably about time that you start to do so. I know that you're shy and insecure and it's really hard to overcome that but if you want something to happen, you'll have to try to get out of your shell. By not putting yourself out there, it is unlikely that anything will go far unless he's actually madly in love with you too and is brave enough to confess his feelings. Since you are asking this question, I assume that he isn't someone who's madly in love with you AND openly shows it so I wouldn't expect him approaching you anytime soon. In this case, don't text him because you have not established a person to person line of communication and it's just kind of awkward to start texting someone you don't really talk to in person. I've also done this before and it just comes off as being super weird and a bit of a stalker because you guys don't actually interact with each other in real life.
I understand feeling worried and self-conscious of appearing foolish in front of the people we like but from what I have learned through my experiences, the little quirks of your personality are what make you interesting and usually what draws people in and make them like you. Although it is important that you are kind and don't do anything offensive, looking like a fool from time to time isn't necessarily a bad thing. And if this guy isn't cool with the little weird things you do, then he isn't someone who you should pursue a relationship with because you can't be yourself around him. Being able to be true to yourself is an important thing in order to have fulfilling friendships and relationships. Putting up a facade is tiring and difficult to keep up so ideally you should find someone who you can just relax around and not have to worry about seeming perfect all the time.
So in general, the advice here is to go talk to him if you haven't already or text him if you already talk to him. Don't be afraid of being a bit awkward or doing weird things because that just makes you more human and mature understanding members of our society typically like people who are more human (unless your awkwardness REALLY hinder you in making connections with people but I'm trusting that it doesn't since you did mention having a friend). It's normal to feel worried and self-conscious but if you don't risk it by putting yourself out there then you'll never go anywhere. This could end up being something really nice or it could end up being something that is disappointing. Whatever it is, those are life experiences and they help you grow as a person.