Checking the phone is a habit, not a decision: the hand moves before you've thought about it. Field studies logging real use show most checks last seconds and are set off by where you are and what just happened more than by any decision. Evidence: decent
A habit runs on a short path. Make the path longer and the hand often stops halfway. Logging out adds ten seconds and one moment of "do I actually want this?". That's usually enough. Common advice, sensible mechanism, no trial of this exact trick. Evidence: worth trying
Deleting the app and using the browser version does the same job with more friction.
Same theme: The phone
The phone
Grayscale the screen
Set your phone to black and white. Android and iPhone both have it under accessibility. Add it to the quick toggles.
2 minEvidence: decent
The phone
Phone in another room
When you need to think, the phone goes where you'd have to stand up to reach it.
no timeEvidence: decent
The phone
Say what you're looking for
Before you unlock the phone, say it, out loud or in your head. "Checking the train time." If you can't name it, put it down.
no timeEvidence: worth trying