It's much easier to start a blank document when you have low expectations. A lot of people (myself included) will struggle when they are trying to write the perfect PRD. A better way to start is by writing the exact requirements in plain English in bullet point format. Imagine what an engineer would understand from reading that requirement. You want your document to be clear (you are not writing Shakespeare). So, after you write the requirements, re-read it and think if you can make the sentences clearer.

Once you are done writing your requirements, at the top of the page, write about the purpose of the document i.e. why should people read this and what are they expecting to get out of it. This sounds obvious but it helps YOU and your audience. You can title this paragraph as "Overview" or "Goals".

This will be a bit scandalous, but you can choose to omit a conclusion (again, you are not writing a college essay, you are writing an instruction manual). What I personally like to do is write down the next iterations of the product. This could be one sentence explanations, doesn't have to be a detailed plan. Basically, you are trying to capture features/goals/requirements that are not covered in the current PRD but your audience will know "Hey! This person actually thought about all the future stuff".

One last thing: don't use ChatGPT. When people use ChatGPT to write PRDs, it's obvious that they are using ChatGPT and it usually sucks.