G'day, mate. What are you up to? Today, I am going to talk about why you're not confident in speaking. It's not simple to say, actually. But here are some of my assumptions based on my experience and experimentation.

1. You're not confident in speaking due to lack of experience. If you are living in non-English speaking country, it's a bit hard to practise speaking. Understandable. But, nevertheless, you can, for instance, talk to yourself wherever you are. It's just the matter of how you should be doing. It's really simple. If you've got already used to all the basic grammar rules, correct pronunciation and vocabularies, there'll be nothing to worry about for you. At first, it doesn't really matter how good or bad you speak. No one listens to your monologue, just practise, practise and practise yourself until you're able to confidently speak.
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3. You're not confident in speaking due to lack of grammar rules. It's simply difficult for you to speak confidently. Grammar rules are not infinite like vocabularies, so please try to get one grammar text such as "Grammar in Use" and review every chapter as quickly as possible. Don't spend too much time for this, because you will surely get bored easily. Just read a key principle of each grammar rule and write a piece of sentence in your own word. That's the key to success in polishing your grammar.
4. You're not confident in speaking due to having a 'fear' of speaking itself. If you think you're also not confident in speaking your mother language in front of people, that makes sense. But if it's not, then your fear might come from something else. Grammar? Pronunciation? You need to find out what's wrong with you. I believe that there is just a slight correlation between your confidence level in English and your mother language. Usually the fear in most cases comes from lack of grammar rules or pronunciation.
5. You're not confident in speaking due to lack of daily input learning. If you don't read English and don't listen to podcasts, then it's difficult to talk continuously. Without any knowledge, how on earth could you speak confidently? Just fantasising? Or beating about the bush with a full of absurdity? You need to at least read some daily news or blogs on a daily basis, so that you know what you can talk pretty confidently. Pretty simple.
6. You're not confident in speaking due to lack of correct pronunciation. If you think what makes you hesitate to speak is this, then why don't you refining this by doing read aloud first? You can easily check your pronunciation via online voice recognition services or just recording yourself and ask someone for checking your voice. Without proper pronunciation, I understand why people tend to hesitate to speak, but of course it depends on where you're from. Many Europeans don't really care about pronunciation, for instance, because of their different cultures or something. Accents are fine, but if the accents interfere listener's understanding, which is problematic.
7. You're not confident in speaking due to having no traumatic experience in English. What does it really mean? It means that you have never had a devastating failure when it comes to your English learning, especially speaking. You should be more like a listener all the time. You subconsciously sort of try to resist initiating a conversation. You need to have a failure as it brings about a new step for your speaking. Get out of your comfort zone! This is a very important process to boost your confident level.

That's all for today. Thanks for reading!

Have a good one, ta.