Random, unstoppable beeping

[frerqoibsgfpoijq]

Last night around midnight, my A52, which was on the charger, started beeping approx 1/sec. After a minute or two, it started beeping rapidly, approx 2/sec. I unplugged the phone and closed all apps but it kept beeping. The only way I could get it to stop was to hold the side button and reboot. Notification settings are all OK.
Any ideas why this happened and how to prevent it? Do you think the midnight time is significant? I had no scheduled calendar events for that time, FWIW.

 

[Dannydet]

Maybe you accidentally set a timer, alarm, or something?

 

[AugieTN]

Did your phone get wet?

 

[mikedt]

AMBER or some other emergency alert?

 

[frerqoibsgfpoijq]

I checked for timers; none set. I've had Amber Alerts in the past and they were MUCH louder and more intrusive. This was pretty quiet, like the beep of a microwave when food is finished.
Is it worth running a virus scan? What app?

 

[AugieTN]

Right now I wouldn't worry about it. If it happens again, I would do a factory reset.

My wife got her Pixel 4A wet and it started beeping and it was just a splatter by the kitchen sink, that's why I asked if your phone got wet.

 

[mikedt]

Yesterday my Samsung Note20 Ultra started beeping when on charge. But I noticed a notification stating that the USB connector might be wet., which it wasn't AFAIK. I restarted the phone, and it's been OK so far.

 

[frerqoibsgfpoijq]

Problem solved, and boy am I ever embarrassed! <insert BIG embarrassed emoji>
It turns out this wasn't my phone at all. The offending device was an electronic weather station that sits on my night table near where I charge my phone. The beep didn't, naturally, cause a vibration in my phone but that just added to the mystery. In my defense, I am hard of hearing and wear hearing aids, which were out for the night. One ear is very bad, so I find echolocation of sounds difficult. The alarm button on the weather device is right next to the brightness control and apparently I'd inadvertently hit that at some point and activated an alarm for 12AM. When the alarm went off again last night, my wife immediately figured out where the sound was coming from. She hit the ALARM button which stopped the sound, and as a precaution unplugged the unit. Well, that only put it into snooze mode and the alarm went off again in 8 minutes, apparently on battery backup. This time, I got up and fiddled around with the unit until I figured out how to turn the alarm off.
Anyway, thanks for your excellent suggestions. I'm only giving this long explanation because, hey, if you can't laugh at yourself, that's not a good thing!