Fenix 7 keeps switching off after asking me to set up assistance

For a few days, my watch has been unable to remain on: it randomly switches off after a few minutes (sometimes up to one hour or so).
Additional context: I made sure it is not a low battery issue by charging it, I already tried switching it off "normally" and then on again but it didn't resolve anything, and this happens without launching any activity, just from the home screen

Before switching off, it displays the following message: "Set up Assistance Using Garmin Connect Mobile" preceded by what I believe is the assistance logo (a white asterisk on a red disk)
Sometimes, before this message, it shows the screen that I usually access after pressing "light" for 1-2 seconds

Anyone encounters a similar issue?
(I'm looking for a solution softer than to reset my watch first.)

PS: Also, brightness seems very low as I power it on again each time, but I'm not sure that it is unusual, and anyway, it's fine since I don't usually do this often.