Sometimes people delay writing. I’m not thinking of work avoidance, kidding yourself that a household chore somehow takes precedence. That’s common, but different. I’m thinking of over-research, spending too long gathering information and postponing the start of actual writing.
It’s a bad idea. Jobs take longer. You risk losing freshness in the writing. The more you research, the further you get into the mindset of the expert and the further away from the readers, the ones who really matter.
You also risk gathering too much material. You’ll then be tempted to make full use of it – a big error, like trying to fit all your food into a single meal.
As a general rule, it is a good idea to start writing sooner rather than later. Even if you know you still have people to talk to or research to do, if there’s a section of the project that you can start writing now, don’t hesitate. Get on with it.