My AirPods mysteriously disconnect from MacBook Pro when I use them

I open the case, and put on my AirPods then I hear a signal that they are connected to the mac and I see the changed bluetooth icon.

Then I open Apple Music or YouTube, Skype etc wherever I want to hear a sound. They work for some time and then at random disconnect and the sound goes from manual speakers on my MacBook.

I have tried different ways to figure this out: I disconnected and connected again, forgot and connected them like a new device, turned off bluetooth on my iPhone. But the problem is still on.