No. I don´t feel nervous but i will be little bit concerned about the message, whether the reciever understand it completely or not. How to overcome, if you are nervous?..mmm...better to ignore the grammatical mistakes at early stage while speaking. I feel thats the first factor to become nervous. Our mind will start to think, "What will others think if i make more mistakes?" and this thought will not let us to speak. Anyhow thats not our mother language and we no need to worry about making mistakes while learning (Even we did many mistakes while learning our native language in childhood). So it doesn´t matter at all. Wish you all the best in your learnings.