Why Did I Do That?

So yesterday at school, during lunch break, I walked past the cafeteria and saw Alex eating alone. You know how sometimes you just feel bad for someone who's by themselves? Well, it struck me that maybe Alex could use a friend. So without really thinking, I decided to go sit with them. But then... things got weird. As soon as I sat down, my face felt hot and my hands started sweating. Why did I suddenly feel so nervous? I've been friends with Alex for ages; it's not like we're strangers. But the moment I sat there, all those butterfly feelings from last year came rushing back. Last year, when we were younger, I had this big crush on them that was just a silly little schoolgirl thing. Now it feels different, but still weird. So here's my question: is it normal to feel butterflies around someone you know well and like as a friend? Or am I overthinking everything again?