froze for 20 seconds in my first mock interview, then just started talking

My first mock interview I got asked to reverse a linked list and just blanked, like actually blanked, staring at the whiteboard for maybe 20 seconds while the interviewer waited. I almost said "sorry can we skip this one." Instead I just started saying out loud what I did know, that I'd need to track a previous node somehow, and that one sentence kind of pulled me back in. Ended up drawing three boxes and arrows and it clicked. Still messed up the pointer order twice. But the freezing part only happened because I was trying to picture the whole solution before saying anything, next time I'm just going to talk first.