The best time to start

...is before you need to.

The second best time is when it's necessary.

And the third best time is after you've stalled long enough.

Thing is, none of these options include 'when you're ready.' Because you almost never are. (Even when you say you think you are. You're not.)

Hence the obvious workaround: if you're never going to feel like you're ready, why not default to starting before you feel like you are?

The thing about 'waiting until you're ready' is that 'ready' is always just another day away.

Starting now--before you're ready--is uncomfortable, but it's only way to ever to start before you need to, which is to say, the only way to ever start at all.