iPhone 8 won't vibrate when plugged in

I just purchased an iPhone 8, and when I plugged it in to charge there was no vibration pattern to indicate that it was charging like there is normally. I had the phone on silent with vibration enabled, and it had vibrated previously when receiving texts, but not when charging. I turned the volume on and plugged it in again and it made the usual 'charging' noise, but nothing on silent. Is this an iOS 11 thing? Please I don't deal well with change help a girl out