You're still not sure of what problem to solve. You're going in the reverse direction: "I wanna startup something, so let me identify problems". This is fine but at this stage, you needn't work on this full-time.
You have to work passively every single day, finding those most burning problems that your skillset can solve. You also need to gather the right folks who can complement your skills, e.g. a Designer, a Product strategist.
Once you have your problems & your lean team, you need to do some research & some product trials to understand your PMF (Product Market Fit). Once you're confident, you can leave your job & pursue this with all the LOVE & CONFIDENCE. Without these two, you'll be shattered by small failures, you'll tend to quit. So, better not to give yourself that chance of turning back.