Realize that it’s going to take you time to get into it, every time. Don’t expect it to come to you right away.
Ease into it.
Here’s a good way: take a step back and just sketch out the scene/sequence/script. Hand-write an outline or a diagram.
It’s not something for posterity, it’s not something you’re going to refer to next week or next month, it’s just an exercise to get you oriented.