You’ll NEVER feel ready to start working on something.
It’s best to just move past this feeling by “switching off your brain;” think of it as going into “action” mode, and abandoning “thinking/feeling” mode.
You can do this by making the work as “easy” as possible. Just say something like “I’ll work for 2 (or even 1) minutes, then I can stop. If I feel like continuing, I’ll do it.”
That 1 or 2 minutes is action mode, and that tiny time limit is hardly demanding. This makes the mental leap to work mode easier to do.
Just like that you’ll probably end up working for at least 10 minutes or more, even if you never actually felt like working to begin with.
Just remember that starting to work is harder than continuing to work, if you can get just started then the rest will take care of itself.