macOS Sierra is constantly displaying an "Enable Siri?" dialog. If I pick cancel it just pops up again 5 seconds later.
How do I tell macOS Sierra to stop asking?
If you've been mistakenly triggering the Siri pop-up when your finger mistakenly hits the top right area on the Control Strip, you can remove the Siri icon.
Go to: → System Preferences → Keyboard, then click the "Customize Control Strip" button on the bottom.
Move your cursor to the Control Strip (which will now be in Edit Mode), and click and Drag the Siri Icon back onto your screen into the area with all the unused Control Strip widgets.
Accept by clicking Enable Siri, then go into → System Preferences → Siri to uncheck Enable Siri. That should take care of it.