Overcoming the fear of speaking a foreign language
Acknowledging the fact that you have a fear of speaking in another language is already a step towards fighting it. And if you are shy to speak to someone, just let them speak instead, as it will put you at ease and make them more supportive and understanding. You can also ask them for help with your fear and maybe they will suggest the best solution.
If you're worried you don't know enough words to speak the language, remember that babies start talking with only one word. The most important thing is to start talking, only then will you see great results. You can work on your vocabulary by making flashcards and practicing on your own: make flashcards not just for single words but for whole phrases and this way you will already have some prepared responses.
Practicing on your own is a great idea. Nobody will interrupt and you will feel more confident when no one else is listening. You might want to get an audio course and repeat after a native speaker which will also give you a clear idea about pronunciation. Reading out song lyrics in your chosen language could be another way of practicing.
Otherwise, you can always hold conversations with yourself, no matter how crazy this sounds, it is honestly a great way of practicing conversation skills and getting physically used to speaking in that language and hearing yourself speak it. You can also try and reply to your family at home in your target language first and then in your native tongue - you and your family will get used to this way of communicating and they will probably be more than happy to help.
Talk to native speakers, they will appreciate you learning a new language and will help along the way; people are always eager to explain and correct your mistakes. Don't be afraid of making mistakes, it means you're trying and learning. No one is going to judge and laugh at you - we have all had to practice our skills at some point.
Put yourself in situations where you have to speak your target language. Go travelling and get lost in an unknown city and you will be forced to ask for directions. It's not as hard as it might seem but in a moment of need you will find the right words. This way will help you fight your fear and not be afraid of it.
Starting talking is the key, no one will laugh and you will be surprised how much support people show when someone is learning a foreign language. Be honest with native speakers when talking to them in their language and they will be happy to help you with your grammar and vocabulary.