Why do my AirTags chirp for a few seconds randomly?

If they detect their own physical movement w/o one of their “paired” AppleID devices being nearby and “on/communicating” via Bluetooth and/or UWB they will do this.

This is a personal safety mechanism intended to alert folks that they are possibly being “tracked” w/o their knowledge.

See:

What to do if you get an alert that an AirTag, Find My network accessory, or set of AirPods is with you - Apple Support

and

An update on AirTag and unwanted tracking - Apple

Again, that behavior certainly “sounds” as if the tags are at times are NOT detecting a paired bluetooth / UWB device. (and movement is being constantly provided by the live, breathing creature)

Although the chirping tag in a room - presumably motionless - is for now inexplicable.

Bluetooth is short range to begin with, and it’s freq is substantially attenuated by moisture (e.g. a dog’s body); and the AirTag is a VERY power-limited device.

This might not be the best application of AirTags; it will only track the dog if he/she is near a “reporting” device.

A dog romping loose in the woods - as mine has done on occasion 😣 - will remain “unlocated.”

You’re welcome … that “non-moving but still-chirping” tag is still an “unsolved mystery” to me though. 🤔