If you don't impose any requirements on it, such as market size, field of activity, starting resources, etc., then it's very, very simple. First, realize whether you are a pessimist or an optimist. If you're a pessimist, just sit down and think about what has annoyed or pissed you off lately. Fixing that will be your startup. Optimists will have a harder time—you need to find a pessimist and ask them what pissed them off today.

I sat down and thought, and here's my quick list of annoying things:
- Poorly and unreliably closing coffee lids;
- Always opening a sauce jar from the wrong side when delivered;
- Cat food pouches that open crookedly and get your hands dirty;
- Apps that, with poor internet, still try to load a downloaded movie or music;
- Apps (like Notion) that use "/ " with the Russian keyboard layout;
- Counting how much coffee I've already drunk at the office to avoid drinking too much;
- Constant model changes in clothing stores (from season to season, the same jeans in different sizes and fabrics);
- Dirty glasses lenses.

Solve any of these problems—write to me, you already have one client)