Love the question.
Here's a thorough answer (I feel like I've enjoyed reading the discussions on here and haven't contributed yet, so here goes my two cents):
I think many of us are in the same boat re: finding the right potential cofounders. I've been looking high and low for the last two months (turning down a number of interested potential CTO's in the process) because I haven't found my definition of "excellent fit." It's so incredibly paramount, and I think it's one of the few things everyone in the startup community agrees on. I can affirm this from the other side of the table - I used to be a VC and we would primarily invest our Series A money in the founding team, or rather, our belief in them to execute and overcome the as-of-yet unseen obstacles in front of them.
The point is that - just like the FounderDating tagline says - ideas change but people don't. Meaning, I guarantee that the idea you have at the moment - whatever it is - is going to morph and evolve and change many times over from now until you find "your engine." The point is having a team that can learn with new market data, and iterate very quickly to find the thing that works.
So my advice is - you can find that person or do initial market research while you have your job. Keep the income and safety net while you still can (as you take the next steps to get ready to take the plunge).
Next I think is the question of why you want to start a startup in the first place. Is it the joy of building things? Not having a boss? Riches? The excitement?
That answer is critically important. It IS exciting, glorious, and consummately rewarding - but having been in a failed startup in the past, I can also equally say that it is arduous, tiring, and unrelenting. I feel that there is always a "grass is always greener" with startups, and my perspective is that it is simply more of everything. The highs are higher and the lows are lower. That said, I firmly hope I never work for another corporate firm again. I love it, and the high potential for failure is dwarfed by the reward I feel by doing it. Just be sure you're up for the whole package, and not the glorified image the tech press portrays.
I think the only real reason not to take the plunge is if you had a family to support. For me, I don't mind if I put my own self in financial jeopardy (what's the worst that will happen? I eat ramen for a while), but that equation changes when others are involved.
That said, I think that once you find your cofounder(s) and have an idea of what you want to do - you should jump in. If you're committed to doing it, you find your partner, and you have an idea you love - jump in. Quit. Take the plunge. Best case you have a wild ride and make money. Worst case it fails and you move onto the next thing. Either way, you did it and grew from it.
My two cents.
Oh, and if anyone knows of any really excellent full-stack software engineers, please send them my way :).
For that matter, I love chatting with just about anyone in regards to startups so feel free to reach out.