iPhone 11 pro max screen randomly began flickering and glitched out?

You may try some of these steps, please check after each step...

1. Sometimes, a simple restart can resolve temporary software glitches. Turn off your iPhone, wait for a few seconds, and then turn it back on.
   1. Restart the device. That's it.
   2. Still not solved --> Force restart iPhone - Apple Support
2. Get a Genius Bar Reservation and Apple Support Options - Apple
   1. When you encounter issues with your Apple devices, the Genius Bar at Apple Retail Stores is the go-to place for expert assistance. The Genius Bar is staffed by knowledgeable Apple employees, often referred to as "Geniuses," who can diagnose and resolve a wide range of hardware and software-related problems. To ensure personalized attention and a convenient visit, Apple provides the option to schedule a Genius Bar Reservation.
   2. Contact Genius Bar. Manage Reservations - My Reservations - Apple
3. Take your device to an Apple Retail Store or Apple Authorized Service Provider, or contact Apple Support:
   1. If you prefer face-to-face assistance, you can visit an Apple Retail Store. Apple Retail Stores are designed to provide a hands-on experience with Apple products and offer support services. You can speak with Apple specialists, known as "Creative Pros" in some locations, who can assist you with product-related inquiries or minor troubleshooting.
   2. In addition to Apple Retail Stores, there are Apple Authorized Service Providers (AASPs) that are authorized to perform repairs on Apple products. AASPs are independent businesses certified by Apple to offer service and repairs for various Apple devices.
   3. If visiting a physical location is not possible or convenient, you can seek support by contacting Apple Support. Apple offers various channels for support, including phone support, live chat, and email. The official Apple Support website provides information on how to reach out to Apple for assistance.
   4. Finally, you can also start a repair log or track the status of existing repairs --> Apple Repair and Repair Status Check - Official Apple Support

In summary, Apple provides customers with a range of support options, including the Genius Bar Reservation system, visits to Apple Retail Stores or Authorized Service Providers, and various channels to contact Apple Support for assistance with their products. These services aim to ensure that Apple users receive the necessary help and support whenever they encounter issues with their devices.