Focus randomly comes on

Hello Donotdisurb,

If a Focus is enabling on its own, it's possible that it may be scheduled to be enabled. Be sure to check on that by heading to Settings > Focus, and then tap through each option here (Do Not Disturb, Driving, Personal, etc.) and check out the Turn On Automatically section to see if that's set up.

There's some further info here: Use Focus on your iPhone, iPad, or iPod touch - Apple Support

As the page notes, "When you turn on Smart Activation, it automatically turns on the Focus at relevant times throughout the day based on your signals, like location and app usage."

Cheers.