Why is the OS installer trying to launch on restart?

I bought a new MacBook Air 2 days ago. I just ran the App Store updates that caught me up on all the apps like Pages, etc. (plus system updates) -- this ran for a couple of hours and required a restart to complete the installation. When the computer restarted, it displayed a screen that said

macOS could not be installed on your computer

The path /System/Installation/Packages/OSinstall.mpkg appears to be missing or damaged.

Quit the installer to restart your computer and try again.

<Restart>

If I simply "Restart" it loops through and displays this screen again. However, if I restart and hold down the Option key it gives me to option to start up from my system HD or from this thing called the installer (and it is the selected item). If I select the system HD then the restart completes and operation appears normal.

However, on the next restart it does the same thing, i.e., it's not clearing whatever state it thinks it's in.

I bought the MacBook new and it came with High Sierra installed, so it's never had any other OS on it nor have I downloaded any installer package (that I know of ... unless it was part of the massive App Store update).

How can I get back to a normal start up on restart?