Hey! I have to do some teeaching as part of my funding, and did second year seminars in my first year and was the TA for a third year module this year. I was really nervous too, but luckily at my uni for the first semester they pair you up with a second or third year PhD student so you are with someone more experienced and not completely thrown in at the deep end! It is a bit scary at first, but it does get easier and it's good for developing your confidence. It's the marking that's the biggest pain! I've also been supervising MSc students' projects and that has actually been quite enjoyable for the most part. So just go with it, it can be nerve-wracking, but it's really good to get the experience to put on your CV and will pay off in the long run! Best, KB