Does a showdown start when you move a unit to a battlefield you already control?

Ruling: No, a showdown does not start when you move a unit to a battlefield you already control.

Nuances:

• A showdown only starts when a battlefield is contested, meaning it has a unit from a player who doesn't control that battlefield
• A showdown also starts when attempting to conquer an empty battlefield (since the unit is at a battlefield it doesn't control)
• You can directly play units from your hand to battlefields you control without triggering a showdown