When do you ask for help vs keep banging your head on it? Terrified of being "that person" who asks too much.

Three months in. If I ask a question I feel like I'm proving I don't belong. If I don't ask, I burn half a day and someone eventually goes "oh yeah that's a known gotcha, should've asked."

Is there a rule people use? I've heard "15 minutes then ask" and also "timebox an hour first." What's the actual norm on a healthy team? And how do you ask in a way that shows you tried instead of just "it doesn't work, help"?