Why is sound shutting off (on Bluetooth or USB) after a couple minutes

Why is sound shutting off (on Bluetooth or USB) after a couple minutes

When I connect the Speaker to the computer (either via Bluettooth or USB) sound plays fine for several minutes and then stops - speaker is still on and still shows Bluetooth connected. When I shut it off, it says discoonnecting & shuts off and if I turn it back on, it reconnects and sound starts again

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