how do you figure out how to start a piece?

i’m sure this question has probably been asked plenty but it’s 5am and i have the burning need to write and…absolutely no idea on how to start this. so! im curious on how others decide the best way to start writing is - how do you just…get a good starting sentence and get going? any tips on it?

i need to get this idea out of my mind but with no starter i’m just a bit stuck.