So many people never start writing — not because they don't have a story, but because they're afraid of writing it badly. The first sentence has to be brilliant, the first chapter has to hook the reader from the very first line, the dialogue has to sound natural on the first try. With demands like that on yourself, it's easier not to open the document at all than to open it and be disappointed.
But a draft isn't supposed to be good. A draft has an entirely different job — just to exist. If there's material, you can fix it: rewrite a line of dialogue, cut a repetition, swap a clumsy phrase for the right one. But you can't fix an empty page, because there's nothing there to fix. A writer doesn't learn to write by composing perfect sentences in their head — they learn by writing actual text. A lot of it, even imperfect text, even text they'll rewrite half of later.
So it doesn't matter where or how you write. In the notes app on your phone, at a computer, longhand in a notebook, on a random napkin if a thought strikes at the wrong moment and that's all you've got on hand. You can even talk it into a voice recorder if your hands are busy and the words are already forming in your head, asking to get out. The form doesn't matter. What matters is that the words exist somewhere outside your head — then you can actually work with them.
So — write. Write badly, write clumsily, write with repetitions and awkward dialogue. All of that can be fixed later. An empty page can't.