If you're that hesitant, maybe you're not actually ready? I'll go against the flow here and say don't do it until you're ready. This journey is about happiness, not about leaving your job.
You can pull that trigger anytime you want to -- but you can't unpull it after that bullet is fired. So be sure. Take some time to figure out why you're reluctant. Imagine sending it, imagine how your boss will react, imagine how you'll feel, imagine waking up on your first day without a job or a plan to get one, walk through the whole process virtually, and see if anything sticks out as a red flag that concerns you.
That old saying, "If it's too hard to make a decision, it's too soon to make a decision," has some merit to it.
It's okay to wait if you aren't quite there yet. You're the only one who knows when the time is right.