I have used the OpenAI API in many of my apps, but currently don't have any startup idea.

Agree with @donmarco Just like to add that when focusing on a problem, focus on problems that either you have faced or you have closely observed 1st degree network facing it. This ensures the following: 1. That the problem is not assumptive 2. You understand the nitty-gritties of the problem thus helping you design a better solution. 3. You can easily recruit early adaptors for your product 4. These early adopter will help you with the following: a. improving product by letting you analyse their experience b. recruit next set of users via word of mouth

My recommendation is to focus on a problem first rather than an idea. Once you have identified and validated a problem, you can proceed to think about ideas/solutions that can fix the problem. Now, if you want to find someone to partner with, YC has a co-founder matching platform where you can find someone based on your preferences for interests, skills, location, and more.