Starting a business is not unlike starting a downsizing project. You are staring down a pile of tasks or a pile of stuff. Either way, you need to pick a starting place.
I'm a big believer in just starting, sometimes indiscriminately. Sometimes with tenacity. Any end of the spectrum is just fine. Once you've passed through that translucent veil, you're in.
The hurdle, really, is simply accepting and, in part, owning the project. To take it on as your responsibility can be daunting. But make that the focus of your internal conversation. Try not to admonish yourself for letting it have gotten this far, or find excuses for lack of time or wherewithal, or believe that there is no good place to start, or persist in the belief that there is a perfect place to start and you just haven't found it yet.
Starting is just a question: do or not do? A sort of "to be or not to be" ... but far less existential.
Take a moment simply to sit with yourself and ask if this is something you want. A goal worth striving toward. And then, just start.