In general, starting with the products you love to use, or looking at where your favorite people you've ever worked with currently work, is probably the best move.

In case helpful, I collected some startups I find interesting, see the startup lists section: https://chrisbarber.co/start-here/.

Though I think the ideal would be:

* What are the products you find most enjoyable to use?

* Of those, which ones do you have ideas for improvement based on your usage?

* Who are the best people you've ever worked with or collaborated with?

* Where do they work today?

Figure out things you are interested, do a bit of learning and reach out to companies in that area. Sounds like you may be early career.

Hackathons in areas you have an interest are great for connections as well.