Yeah, Big 5 is very dry in most presentations - I know I plug Daniel Nettle's Personality: What makes you the way you are like it's going out of style, but the book really helps fleshing the system out and giving it a bit of the kind of feel type and function descriptions give Jungian typology. It's also just generally a very good layman's "serious" intro text to Big Five, I'd say.
Disclaimer: I am not a psychologist. I merely have an interest and am currently studying for a degree in a related field.
I found a "fake it till you make it" approach somewhat helpful. If you take it in baby steps, just putting it on a bit, consciously thinking about body language or how you speak, or what to say. If you feel yourself burning out, just take your foot off the gas a bit, both in the present moment and in the long term, because if you push too hard too fast then you'll end up having a bad night or an identity crisis. It will take time, it will feel like work and it may not even help you honestly, but it may be worth it in the long run if this is something that is bothering you.
In psychology there are 5 fundamental factors of personality, one of which is extroversion. While informally used to mean socially outgoing, extroversion is more accurately understood as how strongly someone feels positive emotion. While this does mean that extroverts are generally more social and outgoing (because the rewards are more worth it for the effort put in/ risk taken) how someone places on the introvert/extrovert spectrum, or any other 5 factor spectrum can be expressed in many different ways.
From what you say it sounds like you are quite introverted and possibly somewhat neurotic (another of the 5 factors) as well. introverted people tend to struggle to connect with others at first, but will form more long lasting relationships in the long run. I find that understanding where you lie on these spectra can be helpful in making you more comfortable with yourself and how you behave and view the world. Everybody loves extroverts because they're more fun at parties, but the world would be a very different and much worse place without people on the other side of the spectrum.
If you want to know more about this, I highly recommend Personality by Daniel Nettle (Amazon link: https://www.amazon.co.uk/Personality-makes-Oxford-Landmark-Science/dp/0199211434 ) He explains in a clear and easily understandable way where the 5 personality factors come from and goes through how where you lie on the scale may affect you. Most importantly though, as he says himself, the aim of the book is to help people understand that they can't change where they lie on these scales (and that in all but the most extreme cases, they shouldn't want to) but that you can change how you express your fundamental personality type in order to be happy and content with yourself.
This one's pretty good, although a little out of date ... although The Bell Curve is even more out of date! There's been tons of research on intelligence in the last 25 years. Here's a good recent scientific book on it.