My thanks to everyone for the replies.
I suspect I'm using the wrong word to describe the problem. (I'm still computer-challenged).
I'm using a desktop.
I have been saying that I have a key that is "stuck." Maybe I should be saying "locked" or "jammed." The keys on the keyboard all look normal, it doesn't look like any of them are depressed downward or physically "stuck." But something must be locked in place or jammed. Probably something to do with the "h" key. The monitor shows five or six lines of the letter "h" in sequence and then goes bonkers.
I can recall this happening several months ago when my daughter was using it. My son (not available) came to the rescue. I think I overheard them saying he pressed some certain keys in rapid succession to correct the problem.