If you don't have enough saved for retirement, you'll need to determine what you're going to do next. Make sure it's something you're passionate about.
Running a business costs money. Make sure you have the funds available before you quit your job. You need to be financially prepared to pay upfront and make money later.
How much time do you want to devote to your business. The sooner you want to be profitable, the more time and money you have to put out upfront.
Is there a chance you want to start a business and still keep working? That's ok. Find a business that works for you and minimizes the amount of debt you accumulate.
You may have a fantastic idea, but how much experience do you have. Do your homework before you quit your job? When you're the boss, you're responsible for everything.