https://fixyourandroid.com/how-to/fix-phone-vibrate-for-no-reasons/
If your Android phone vibrates randomly without any reason, it could be due to system issues, buggy apps, or malware. Notification overload, system settings, hardware issues, and physical damage can also cause random vibrations.
To fix this issue, you can restart your phone, check notification settings, turn off all vibrations in settings, force stop open apps, enable safe mode, fix system issues, perform software updates, update apps, or as a last resort, factory reset your phone. Make sure to back up your data before doing a factory reset.