keyboard disappears on iphone

I had an iPhone 8; I now have an iPhone 13 (it's brand new). On both phones, the keyboard will inexplicably not appear when I touch a field into which I want to enter text. With the iPhone 8, I could sometimes reboot the phone and it would rectify the problem. But, it just happened to this new phone and rebooting has not fixed it.

I saw an earlier post about a disappearing keyboard, in the email app, and the fix was to turn on Full access to keyboards in Accessories. In my phone, it doesn't seem to be isolated to just one app; I encounter the problem in my browser and other apps, too. I've turned on Full Keyboard Access in Accessories.

However, after letting the phone rest and not doing anything that I would expect to fix it, the keyboard has reappeared.

Any suggestions?