My Samsung laptop occasionally reports ata errors at boot time. Typically it looks like this:
The number shown here as 32768 varies but values tend to recur. Afterwards everything is fine.

Yesterday however, it gave a string of errors, and failed to mount the drive at all (which of course meant that most of the commands invoked by the startup scripts failed because the programs could not be found). Also no logs could be written. I tried to transcribe what I saw on the screen by hand but wasn't fast enough.

I have booted it twice since then with no startup errors at all. I ran a short smartctl test yesterday and a long one today. No errors were reported in the log, and the expected lifetime of the drive is given as over 1090 hours. I only have it on for an hour or so now and then as it's not my main machine, so that's a long time calendarwise.

Should I be worried?

No. You can decide if you want to wait (as long as it works/expected lifetime??) or do a backup and replace it. But you can check if the disk is plugged in properly. If it was an old laptop you probably need to clean it up.

Also consider it may not be the disk that is the problem, but what it's connected to - all the components are subject to degradation/failure.

The laptop was second hand but I bought it from Computer Exchange, not directly from the previous owner, so I presume it's been refurbished. I bought it only because I wanted to learn how to use one, and I still can't take it seriously as a computer. It feels like a toy. I use it mainly as a backup device for my desktop. However as it runs AntiX and I don't have Debian on the new desktop, I have transferred the family database (running under Gramps) to it as well. That was backed up yesterday!

I'm going to let the matter rest for a while, but if I do get another failure, I hope I can get down more of the output. I suspect the actual fail messages will be a lot more informative.

when did you buy it? probably better to return it.

A couple of years ago now, way out of guarantee. I just found the original invoice: March 2016. It's always been a well-behaved little machine apart from these occasional ata tantrums. I even once made a Linux From Scratch on it, though I could never get the screen to work properly after waking from sleep (funnily enough this does work in AntiX).