Congratulations on your new iPhone X! After reading your post, I see that you're having some trouble getting it to stay connected with a few of your Bluetooth devices. I'm happy to help!
Based on what you've described, I would recommend using the steps in the following articles: If you can't connect a Bluetooth accessory to your iPhone, iPad, or iPod touch - Apple Support and Get help connecting your iPhone, iPad, or iPod touch with your car stereo - Apple Support .
Thanks for stopping by the Apple Support Communities. Have a great day!