one
It's dead. The Bluetooth headset runs on battery power. If the battery is out of power or damaged, it will often disconnect automatically.
two
The interference source is too strong Bluetooth headset is working at 2.4g frequency, this frequency also has wifi router, cordless phone and 2.4g mouse and so on. These are relatively strong sources of interference.
three
The quality of the headphones is not good, especially the refurbished headphones, which have just been bought normally, and have problems for a period of time.
four
Some Bluetooth headsets, used in other brands of mobile phones, sometimes automatically disconnected.