So, bluetooth was disconnecting sometimes, but this time it has vanished completely, where can I install it again?
Try to enable the display of hidden devices in the device manager. You will most likely find a bluetooth device.
I found it in device manager hidden, I deleted it and restarted see if it will be reinstalled automatically. But now there is no bluetooth in device manager.
The intel driver and support assistant shows no bluetooth on the system only wifi card.
Try to use snappy driver installer \ DriverPack solution. Usually, these programs help with disappeared devices. But do not update other drivers through these programs.
Also you can boot from WinPE and check if bluetooth appeared or did not appear in the manager to make sure that the problem is in the drivers.
Sounds complicated, plus even if somehow I will be able to get bluetooth back it might disappear again, and it was turning off by itself, so it’s just a flaw of this device in my opinion. Since I got an extra pcie port I ordered this Intel Wireless-AC 9260 Internal WLAN/Bluetooth