I also noticed this problem.
Simple requests used to take no more than 20 seconds, but now with GPT-4o-mini, they sometimes take 1 minute or more.
It doesn’t always happen, but when it does, it seems to be stuck on the OpenAI server side. I’ve even experienced this issue while using the playground.
btw, I’m using the OpenAi Assistant.
There’s a partial answer for that here:
OMG How gpt-4o-mini can be so slow? - API / Feedback - OpenAI Developer Forum