Yesterday I got my FP3 working again following @Pilo11 's steps in this post.
I also disabled Google updates as @anon9989719 suggested in this post.
I note under Google play store I have > Advanced > Modify System settings > Not allowed.
My phone then worked for the rest of the evening. Over night I turned on flight mode as I do every night. Then in the morning I turned off flight mode and started browsing this thread to see whether there was any news regarding this issue. Within 5 minutes the reset loop started again.
I now reapplied @Pilo11 's and @anon9989719 's advice. In addition I also disabled Google Play Store background data usage as @Jonibhoni suggests in this post and disabled automatic updates in Google Play Store as described here.
Let’s see how long this fix lasts. Thank you all for your helpful contributions!
EDIT:
24 hours later my phone is still up and happy. In addition to the steps above I also completely deactivated Google Play Store in the App info (long press the Google Play Store icon and then press the circled i to access the App info).