You start with a problem, or an inconvenience.
It could be the weather, or something you are used to but (by gosh) is really painful (like high heels), or something that you cannot control (like your weight, or the bulging of your tummy).
That’s right. Start with you.
Then you search for an available solution online (information literally is at the tip of your fingers).
But there is none.
There’s your opening. You have a need for a product. And chances are, there are a lot of people like you searching for the exact same thing, or if they don’t know it yet, they will recognize their need once you get your product out into the market.