The viva is questions: your examiners want to talk to you about your research and there’s 101 things they could want to know.
The viva is answers: if you don’t talk about your research you’re not going to get very far.
It’s 100% fine to pause before answering – questions deserve a little thought at least, not just an automatic response – but social conditioning tells us that we have to answer as quickly as possible. In workshops people say things like “Won’t my examiners think I’m rude if I pause?” and “My examiners will think I don’t know anything!” Either could be true if you were pausing for minutes, but we’re talking about seconds.
Still, sitting in silence in an exam like the viva can be uncomfortable. I like Dr Claire O’Callaghan’s suggestion in Episode 27: take a big bottle of water to sip after each question is asked. That way you can take those seconds to get the question straight in your mind, start thinking about a response and answer well.