Apple has changed the button combinations for both Emergency SOS and a force restart on the iPhone 8 and iPhone X. This gave me quite a fright when I needed to restart my iPhone X, only to trigger Emergency SOS by mistake.
On the iPhone 7 (and earlier), Emergency SOS is triggered by pressing the Power button five times. On the iPhone 8 and iPhone X, it's now triggered by holding down either Volume button and the Power button at the same time.
Sound familiar? The button combination to restart an iPhone 7 is holding down the Volume down button and Power buttons. Out of habit, that's what I did. At least I know how loud the siren is for Emergency SOS.
The button combination to restart an iPhone 8 or iPhone X is now a little more complicated, as Apple's support article on the subject explains:
On an iPhone X, iPhone 8, or iPhone 8 Plus: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then, press and hold the Side button until you see the Apple logo.
New iPhone 8 and iPhone X owners, keep that in mind.