First and foremost, congrats on taking a huge decision for moving into UX roles and good luck
IMHO, in order to learn UX you don't have to quit your current job, you actually need your current job to practice some aspects of UX. I believe being a UX designer is not just having a title and working with developers. In UX, more than everything we should all be able to initiate teamwork, user research and think about users' daily life. We need to learn about empathy, how business processes are working and what makes a better conversion rate in a solution.
You actually have this opportunity to learn as much as you can from the environment around you, and at the same time you can enroll in an online UX course (like the ones presented by designlab) and use your business questions to practice UX. If you want to be a great UX designer, you need to practice to make sure that your thought process is also ready for that. So prepare yourself for a much better job that you can get hired for today. Learn about Lean UX and Design Sprints, you don't necessarily need to be a UX designer to go after these topics, I believe everyone who works in an agile product development should learn about them.
There are a lot of things that you can learn while you still have your job. This gives you an opportunity to apply your UX mental model into your current job. Then when you go for your first UX interview, you have a lot to say and present. If I want to hire a UX designer for my team, I don't necessarily hire them based on their years of experience, it's all about personality and process. If you can learn what is a good applicable UX process for product development, you can apply it everywhere that there is an interaction among a group of users, a brand and you.
In a nutshell I believe you still need your current job as a platform to practice the new knowledge, as you are gaining them.
Good luck and have a lot fun learning about cool UX stuff.