My iPhone crashes after the update IOS 16.1.2

Hello owais11,

There are a few things we will want to check as far as the performance of the iPhone is concerned.

The first thing we would confirm is that all the apps installed on the iPhone are up to date. Here is how: How to manually update apps on your Apple device - Apple Support

You also want to make sure the iPhone has enough storage. Based on the information outlined at About iOS or iPadOS performance on your iPhone, iPad, or iPod touch - Apple Support, you will want to be sure there is always at least 1GB of free storage:

If your device is low on storage, iOS or iPadOS automatically frees up space while installing an app, updating iOS or iPadOS, downloading music, recording videos, and more. iOS or iPadOS only removes items that can be downloaded again or that aren't needed anymore. 

You can check your device's storage in Settings > General > [Device] Storage. For best performance, try to maintain at least 1GB of free space. If your available storage is consistently less than 1GB, your device might slow down as iOS repeatedly makes room for more content.

If you need to free up some space, follow these steps to turn on the storage-saving recommendations built in to iOS or iPadOS:

1. Go to Settings > General > [Device] Storage and read the recommendations that iOS or iPadOS might provide.

2. Tap Enable to turn on a recommendation, or tap a recommendation title to review the content that you can delete.

If you don't see any recommendations—or if you need to free up even more space—you can review the apps on your device. They're listed on the same [Device] Storage screen along with the amount of space that they use.

Tap an app, then choose from the options:

• Offload the app, which frees up storage used by the app, but keeps its documents and data.

• Delete the app, which removes the app and its related data.

• Depending on the app, you might be able to delete some of its documents and data.

Learn more ways to optimize your storage.

After implementing those steps and information, if you are still having an issue with the iPhone restarting, we would go through these steps: If your iOS or iPadOS device restarts or displays the Apple logo or a spinning gear unexpectedly - Apple Support

They can help resolve restarting issues.

Have a good day.