Weird characters after updating OS

[Krystyna Lagowski]

Hi everyone! I sure hope someone can help me out with this strange problem. After I did my latest update, my macbook pro started acting strangely. It was as if it had become possessed. When I start to type, I get a small screen above the line showing me options for that letter in different languages. It then advances forward or deletes backward. When I try to open a new window, I get about six or seven in rapid succession. How can I exorcise this gremlin? This happened to me last time I updated a couple of months ago.
I have a MacBook Pro, M2012, 2.5 GHz Intel Core 15 and am running OS Mojave 10.14.3
I videoed the gremlin in action as screen shots are impossible! Tried to upload the video but can't figure out how to do it, sorry.

 

[Dennis74]

The screen you refer to is triggered by pressing and holding down a key, allowing you to use variations of that letter. Just make sure you don't hold down a key for too long.

 

[Krystyna Lagowski]

Thanks, but I'm not holding down the key for any length of time. And it only happens after I upgrade. It seems to have disappeared by itself after a couple of weeks. Digits crossed.