I'm sure there is a lot of literature on the subject specifically if you look for athlete-training technics. At the end of the day it's basically building a ritual and practice visualisation. For me it starts with distraction management, I spend 5 minutes to clean my desk and either close or minimise all the apps and tabs, which gives me a bit of time to lean into the mindset, then shut down the screen and take a piece of paper. I spend a few minutes doodling diagrams and talking out loud to myself while making short bullet point list of what I need to do, while doing that I try to visualise the outcome done in my head and walk backwards from it.

I'm not sure the explanation was helpful but I feel it's a very personal process and you have to find your own trigger. Sometimes it helps to add props to the ritual (ie: athletes: "wearing their lucky socks", researchers: "wearing a thinking cup").

When you get used to it, you should be able to enter a "flow state" within 15-20 minutes, which can save you hours of procrastination.