The most common reasons an iPhone keeps vibrating for no reason include hidden or silent notifications from apps, certain accessibility settings, email alerts, and software bugs. Sometimes, apps send silent alerts that do not show visibly but still trigger vibrations. Accessibility features like vibration alerts can also cause this. Email set to Push or Fetch mode may trigger vibrations for new mails. Additionally, software glitches or incomplete updates can lead to random vibrations. Other causes could be hardware issues such as a malfunctioning vibration motor or loose connections, especially if the phone has been dropped or exposed to moisture. Rogue or buggy apps running in the background can also cause random vibrations. Checking notification settings to ensure visual alerts are enabled, updating iOS and apps, restarting the iPhone, and removing suspicious apps often helps resolve the issue. If the random vibrations occur when plugging in cables or accessories, faulty cables may be the culprit. Steps to troubleshoot:

• Check notification settings and allow visual alerts for apps.
• Review accessibility vibration settings.
• Adjust email fetch and push settings.
• Restart or force restart the iPhone.
• Update iOS and all apps to the latest versions.
• Unplug cables and accessories to test.
• Remove any suspicious or recently installed apps.
• If issue persists, hardware diagnostics might be needed.

These methods address the usual software causes and can often stop phantom or random vibrations on an iPhone.