Dock is in top row, Here are my settings:

Size nearly all the way to small
Magnification in the middle
Position bottom
Minimize using Genie effect
Prefer tabs when opening docs, Always

Then I have checked
Double-click a window's title bar to minimize
Minimize windows into application icon
Show indicators for open applications
Show recent applications in Dock

Try these settings and see if it fixes. Good luck! Stuff like this drives me batty.

Edit to add: If that doesn't fix things then check settings in Accessibility. That has keyboard shortcuts for zoom and maybe something is set that you actually use? You could just unclick to not have that be an option. There is also Zoom Style (mine has full screen, not even sure what it does)

We'll see if anything changes.

If the other suggestions don't work, here's a more brutal fix:

1) In Finder, use to the "Go" menu and then "Go to Folder" commands to go to "~/Library"
2) You should see a lot of files and folders, one of them will be the "Preferences" folder, open it up.
3) You should see "com.apple.dock.plist".
4) Drag it to the trash and logout and login again.

Warnings:

1) this is deleting your dock preferences, so the dock will reset to the macOS default. You'll lose
any customizations you've made to it.

2) there are lots of files in ~/Library that are not safe to delete. That's why it is "hidden" by default and
doesn't show up unless you use the Finder's "Go to" menu to go into it.

Hope this helps

In such detail to this problem.

I just hope it helps! I spent a lot of years at Apple working on bug reports ... and old habits die hard

Mahalo!

Because it wants my password.

I don't know what the darn password is! I never need it to use the computer. I may have set one years ago when I got this iMac, but it's long gone out of my memory bank. I've tried a few common ones, but no luck. I could do that for a month and never hit it right.

I vaguely remember my son telling me that I didn't need a password, since no one other than me uses this computer. Obviously --- for some things --- I do need one.

Here are two articles by Apple on how to reset your password:

If you are running Catalina (version 10.15) or newer:
https://support.apple.com/en-us/HT202860

If you are running an earlier macOS (10.14 or earlier):
https://support.apple.com/en-us/HT211672

You can check your version number with 'About this Mac' in the menu bar.

But ... this procedure seems the easiest!

https://osxdaily.com/2021/05/11/how-reset-macos-password-terminal/

Good luck!

How far are you from an Apple Store or a trusted third party Apple Reseller.

That enlarged dock is gone, but so are all my current jobs (anything after my last back up in April) and any other jobs that I did since then. .

Also gone are any new fonts I added after 2014 -- and there were dozens and dozens of them.

I'm sure that I will find that I'm missing other items too. It's too depressing to even look. I did find some very old files under "recents". Years old.

Cloud Watcher did his best to see if he could figure out how to retrieve the files, but no luck.

(As to an Apple Store, there's one about 10 miles from me. The last time I was there, they had zero luck in starting my older iMac --- which had that awful "circle with a slash through it" display when I tried to start it.)

This shows what apps are running.
Command+ Tab will bring it up, and holding the command key while tapping the tab key will scroll across to each app, which you can bring to the front and start using, or command-Q to quit the highlighted app, if you like.I use it all the time, but mine does disappear almost immediately if nothing done with it.

It has it's uses.

OMG of course it is! I was stuck thinking it was a problem with the dock.

The problem is most likely a sticky "Command" key so the switcher is coming up when the key is stuck down and the the OP hits tab.

The Command +Tab task switcher should automatically disappear as soon as the Command key is released, but if you hold it down (or it is stuck down), it does what the OP describes, including disappearing when you click away from it.

For what it's worth, I use the built-in utility "Show Keyboard Viewer" to check on sticky keys. You enable it by:
- System Preferences, Keyboard preferences
- Input Sources tab
- "Show Input menu in menu bar" checkbox on the bottom of that window

Once that's enabled, then up in the menu bar there will be a tiny icon that when clicked will show the menu to:
- Show Emoji & Symbols
- Show Keyboard Viewer
-------------
- Open keyboard preferences

Selecting "Show Keyboard Viewer" brings up a small window with your keyboard layout displayed. And it will highlight each key as it is pressed.

The keyboard viewer window is designed to let you preview what you might get when the option key is pressed (it shows all the symbols on top of the keyboard image), but it's also very useful for diagnosing sticky keys on keyboards.

Bringing the window up and hitting command a few times should show if it's always showing released or only sometimes. And we still don't know if it's left or right Command key that's sticking.

A sticky/broken Command key on a Mac is basically hell. I'm kind of surprised the Command+Tab was the most visible problem.

[Disclaimer, the instructions above are for the latest macOS. The keyboard viewer has been around forever, but the way to display it has changed a little over the years. Your system might be a bit different.]