"Scared" sensation in chest

I get a feeling in my chest that is the same feeling as when you are suddenly startled or surprised. There is no pain. It lasts for about 10 seconds. It happens every night when I lay down. Any input as to what might be causing this would be greatly appreciated.

There are lots of causes for this, and my mind goes first to adrenal issues, panic, etc. but there's a mechanical possibility I hear about more rarely. My partner gets this feeling from having a misaligned rib; this happens because of posture issues, injury, chronic tension, deconditioning, inflammation, and other issues. It can be misaligned on the back or along the sternum. For years he'd have a chiropractor or craniosacral therapist pop it back into place, but he's figured out how to do it on his own. There are products like foam rollers and Backpods that can help, and also a yoga practice: sit up straight with your hands laced behind your head, take a deep breath, bend to the left (pointing that elbow toward your left outer hip) and exhale, breathe in deeply again and return to center, and repeat on the other side. My partner will wake up in a panic, heart racing, or just have it come in a sudden wave seemingly randomly throughout the day. For years he thought it was regular panic, but I like to mention this example because sometimes something mechanical can trigger the nervous system in the same way that panic does.