Lol I'm in almost exactly the same situation, and I have before
I would suggest waiting a little longer, until you're absolutely positive that you like them and they like you. From there on, I would recommend trying to give them hints that you like them, and try to make them increasingly obvious until one of you guys asks the other out
But kinda funny story I have a crush on one of my friends and they act nervous around me but not around other people like her brother or some other people,