If you want, allow cake to thaw out a little in the fridge for about 30 minutes to an hour before serving (so that it’s a little softer — that’s how I like it personally). If you leave it in the fridge for longer than that or at room temperature it’ll become softer, and while it’ll still hold its shape it will be a little harder to cut gracefully, but it’ll still tastes amazing — so up to you.