The other way to put up your question is "What's the best time to quit a job and don entrepreneurship hat?". The answer is, there's always a good time to start. Just make sure you don't put your legs on two boats at a time. In time of crisis you'll end up in water, losing foot hold on either.
The transition will be smooth only when you sit down and invest some time to plan your business. And, that can't be done as long as you don't have that passion to live your dream.
Entrepreneurship is living a few years of your life like most people won’t, so that you can spend the rest of your life like most people can’t. Make sure you're ready to live that life.