You can often tell if your mirror has a camera by doing a few tests such as the light shine test or the fingernail test.
To check if your mirror has a camera using the light shine test, shine a flashlight on the mirror from different angles or turn off all lights in the room and look at the mirror closely for any possible indicator lights.
To check if the mirror has a camera with the fingernail test, place your fingernail against the mirror and then see if the reflection touches itself.
If the reflection touches itself then the mirror is coated and could have a camera hidden behind it.
If there's a gap between your finger and the image, it's a real mirror.
If your finger and the image touch tip to tip, there might be a hidden spy camera in the mirror.
Also look around the room and around the mirror and behind the mirror if possible and look for any possible wires or small holes in the wall or random wires that don't look like they belong there.
If you're in a reputable hotel or motel then there will likely not be any hidden cameras although in a private air bnb their could be but also unlikely.