Android
Turn Notification Vibration On or Off auf Android
Notification vibration on Android runs on its own switch, separate from media volume, ringtone volume and Do Not Disturb. That is why muting your phone does not always stop the buzzing, and why turning sound back on does not automatically restore the vibration you expect. The setting controls the haptic pulse that plays whenever a notification arrives, independent of whether the notification also makes a sound.
To change it, open Settings ➔ Sound & vibration ➔ Vibration & haptics ➔ then enable or disable Notification vibration.
Turning this off stops the buzz for every app that has not set its own vibration behavior, while leaving ringtones and alarms untouched. Turning it on brings back a short pulse for incoming messages, emails and app alerts, on top of any sound that is already playing.
If only one app vibrates too much or too little while everything else feels fine, the fix usually sits in that app's own notification channel settings rather than this system-wide switch. Also check that Do Not Disturb or a Focus mode is not silencing vibration on top of this setting, since some Focus profiles suppress both sound and haptics regardless of what you choose here.