Hey 

Well i think you shud just go talk to her...Dont expect it to lead into something serious.. just because your eyes met and those 4 secs u felt something doesnt neccessarily mean it will lead to a relationship. So just be confident and talk to her.. may be u can just introduce yourself and talk abt the class for a bit.. then depending on ur response, you probably will get a hint of what u guys shud talk about and see where things go from there.

Good luck :)