Just started today and am confused. I see boxes with shields around them when running COs, but.... How to open them. A couple times I saw a trigger to run onto to drop the shields, but often I don't see anything. Help please.

Almost all shielded boxes will have a button somewhere nearby, sometimes hidden underneath something (like the tall grass in the Forest). There are a few, however, that have different requirements; in the Abandoned Mine, Floating Continent, and Underground Tunnels, there are some that are locked by a nearby hexagon that has to be hit multiple times to deactivate the shield, and in the Desert and Floating Continent, there are some that are only accessible via the Tornado weather effect.

TYVM Much obliged.

You're not really missing much by not getting them. Sometimes there are half way descent discs or Grinders in them but you can probably get more by running between spawn points.