Is it necessary to update DNS records when changing to Cloudflare?

Generally, you don't need to update DNS records *immediately* after switching to Cloudflare. However, you'll need to configure your DNS records *within the Cloudflare dashboard* to point to your website's IP address or other desired locations (e.g., for email, subdomains). Cloudflare automatically handles the configuration, but you need to define what you want your website and other services to resolve to.