Natural gestures are basically the aim for any public speaker.
We watch an excellent speaker, and maybe we notice their gestures.
I said "maybe" because if he or she is an excellent speaker, we should not be noticing their gestures. We should be taking in the whole package as a message,
without noticing how it is done.
A major measure of excellence in any sort of craft, of course, is not noticing how it was done, unless we deliberately look or search..
If you suspect that are not a natural gesturer, ask yourself
"Is this a cause for concern?"
What does it mean to be "not a natural gesturer"?
Probably this is a person who is self-contained and does not need to gesture to keep their brain functioning or the speech flowing.
Not a person of flamboyance.
Why does it matter?
Get a second opinion, and a third and a fourth if necessary.
It may be that you are communicating successfully without many gestures.
If the feedback says that you need to improve -
and the reason given is that your presentation feels wrong, or rigid or unnatural
(NOT for the reason that it doesn't fit a set of rules that someone feels should be followed for no other reason than that they are rules),
then you can work on them.
The first step to take is to learn to stand with your arms wide open.
Get comfortable doing that.
Feel grounded doing that.
Feel yourself expand out to the audience doing that, while remaining grounded and in your own space.
Once you have established that feeling, it may be a simple progression to loosen up and become expansive with gestures,
flowing along with the emotion and flow of your speech.
If not, then you can learn to gesture - there are any number of general styles and specific movements that I have shared with clients over the years, but those who needed them were quite few.
Find the gesture,
then practise it, and practise it, and practise it until it becomes natural and flows with the language it supports. If it is not natural or flowing, keep practising until it is does, because otherwise it will look incongruous and you may as well have not gestured at all.
I remember my days of representing my high school in competition speaking and being coached to put my finger on my nose when talking about people putting on sunscreen.
For days it felt weird, contrived, uncomfortable.
Eventually, though, with days and days of practice and a supportive teacher-coach, it became natural and I could produce it naturally.
It felt good.
It felt right.
It felt appropriate.
And furthermore, having relaxed through that performance, gradually, I learned to relax into natural gestures.
That was a child, nervous, aware of a very critical judgement as she spoke, and aware, too, of the people who had put in so much effort so she could win for them and the school.
With adult clients, I find those who need some guidance to "loosen up", generally do so quite naturally as they learn to believe in themselves and their message, along with the practice of standing with open body language and relaxing.
If you speak with passion - for your subject and for your audience's outcomes - your body will support your message.
Even if you make no gestures, your stance, your facial expressions and your eye contact, will work powerfully to support that passion and your message.