Issues with bluetooth on iphone 11

Hi, I’ve got an iphone 11 with IOS 15.4 and am having trouble with bluetooth. Every time I connect a new device, I can’t play music out of it for 20-60 seconds. When I go into the control menu and press the audio out button (not certain what this is called) it just says I can select between “iphone” and “speaker”. If i select iphone nothing happens and if I select speaker sound plays out my iphone but neither play from the actual device I’ve connected. This usually resolves itself after 20-60 seconds and it reverts back to “iphone” and “UE Megaboom” (or whatever device i have connected) and operates as normal. It’s not an enormous issue but is quite frustrating, does anyone know the reason?