Your iPhone vibrating for no reason is usually caused by software-related issues or notification settings, but can also stem from hardware problems. Common reasons include:

• Notifications from apps that vibrate without showing visible alerts. Some apps or system alerts generate silent or background notifications that trigger vibration without a visible banner or sound.
• Buggy or rogue apps running in the background that may cause unintended vibrations.
• Software glitches, outdated iOS versions, or incomplete system updates causing phantom vibrations.
• Vibrations when the iPhone is plugged in for charging, sometimes due to faulty charging cables.
• Hardware issues like a malfunctioning vibration motor or damaged components, especially after physical damage.
• Specific settings or features that trigger vibrations, such as haptic feedback or system alerts.

To fix this issue, try these steps:

• Restart your iPhone.
• Update iOS to the latest version.
• Update all apps.
• Check and adjust notification settings to disable vibrations for certain apps.
• Disconnect any accessories and try a different charging cable.
• Delete suspicious or unknown apps.
• Reset all settings if necessary.

If the problem persists after these steps, it may be due to a hardware defect requiring professional repair.