Like all skills, public speaking can be improved with deliberate practice. If you want to be good, you have to do the reps.
One change at a time
My suggestion is to adjust only one thing at a time. Perhaps you notice your shoulders tend to slouch, or you are trying to introduce more narrative into your technical talks.
Start by adjusting whatever is easiest to fix. If you notice you tend to lean backwards 5 minutes into the presentation, make a mental note - at slide 3, check posture. Take advantage of the easy wins first, as these will build your confidence.
Where to practice
There are many opportunities to practice public speaking. Public speaking is scary, so it is important to practice in a space your feel comfortable with.
There are many chances to practice at work. You might consider delivering the next Engineering team update at the all-company meeting. Even if you are not the CTO, why not ask for a guest spot?
Meetups are always looking for new speakers. Give a 5 minute lightning talk on a topic you are passionate about. I'm sure there is a talk idea in your head already.
If you enjoy watching comedy, consider taking a comedy class. Writing stand-up routines and performing improv in teams are excellent ways to practice public speaking. I have learned so much from classes and performances.
There might be a way to quietly practice public speaking alongside your current interests. For example, I recently started playing Dungeons and Dragons and noticed it was using the same skills as improv comedy. All RPGs are an excellent way to have fun and also practice communication skills. If you enjoy D&D, try and DM a one-shot game.
Do the reps
There is no substitute for speaking on stage. Articles and talks about public speaking can only take you so far.
Public speaking is scary and awkward, but please keep practising. You will notice dramatic improvement in only a few attempts.
Keep going, and I am sure you will be proud of the result.