In the book, The Educated Imagination by Northrope Frye, he proposes that almost nothing is original anymore, and that most ideas or stories have already been thought of. It is very rare that someone thinks of something that is completely new and original, that changes the way we all think.
New ideas, especially now, usually only come after you are an expert in a field, or by combining many different fields that you are knowledgeable in to create something new. This requires years of study - often in multiple areas - in order to become competent enough to even begin to know where to start with developing new and original ideas.
For this reason, you are most likely not going to have your own original ideas, in the sense that it has probably already been done before. Rather than attempting to derive new ideas that may already exist, it may be better to just learn about the ideas that already exist.
This can be done through reading books, watching quality videos, attending educational lectures, and talking to interesting people. Ideally, ideas should come from a diverse range of sources. This should be an active process, where you question everything and constantly debate with yourself and others the many different perspectives. If you are not constantly updating your views and opinions, then it probably means that you are staying within your comfort zone.
However, all of this does not mean you should give up entirely on attempting to develop your own ideas. Exposing yourself to as much knowledge and as many ideas and experiences as you can is like a prerequisite for developing new ideas. You have to know what the rules are first before you start breaking them. At the very least, you will immediately know if any ideas that you do have are original.
Through this exploration, you will begin to gain certain insights about your thoughts and ideas that you have never had before. These thoughts and ideas are what can potentially be your own unique and original ideas.
The more you do it, the better you get.