I may have a similar problem with Xperia 10. I have just discovered this thread and actually thought my issue was linked to the “Situations” application.
During the night, the situations application turns the ‘flight mode on’ on my phone, and in the morning, maybe in 20-25% of cases, when the application puts the flight mode off, bluetooth is not back and is impossible to turn on. I am using the application for ages and this is quite recent (some months…) even though I cannot remember when and which SFOS or Situations update triggered it.
When I have the problem, I usually deactivate the ‘situations’ application and reboot. Then I reactivate “situations” and all is fine for some days. The issue never happens during the day even though I am usually connected to a pebble watch all day long.
I can try to restart bluetooth services next time it happens to see if it solves my issue.