If your iPhone 12 or 12 Pro vibrates abnormally, it could be due to several reasons.

Here are some possible causes and solutions:

1. Software issues: it could be due to a system bug.

Try restarting the phone by pressing the power button and the volume button simultaneously.

If the problem persists, you may need to perform a factory reset.

2. Conflicting apps: some apps may cause vibration issues.

Try uninstalling recently downloaded apps and check if the problem persists.

3. Vibration settings: make sure the vibration settings are correctly configured.

Go to Settings > Sounds & Haptics and check the vibration settings.

4. Hardware damage: if the problem continues despite the previous solutions,

it could be due to hardware damage. In this case, we recommend contacting Apple support

for assistance and possibly replacing the vibration motor.

Always remember to back up your data before performing any operations on the phone.