13 pro max display issue

Hi bhaumik243,

Thanks for posting here in Apple Support Communities. What's you're describing can be expected behavior when your iPhone gets too warm. The following article can address the issue you're facing. See: If your iPhone or iPad gets too hot or too cold – Apple Support (AU)

If your device gets too warm

iOS and iPadOS devices have built-in protections to prevent overheating. If the interior temperature of your device exceeds the normal operating range, your device will protect its internal components by attempting to regulate its temperature. 

Avoid these conditions and activities because they may change the performance of your device:

* Leaving your device in a car on a hot day.

* Leaving your device in direct sunlight for an extended period of time.

* Using certain features in hot conditions or direct sunlight for an extended period of time, such as GPS tracking or navigation in a car, playing a graphics-intensive game or using augmented-reality apps.

If the interior temperature of your device exceeds the normal operating range, you may notice these changes:

* Charging, including wireless charging, slows or stops.

* The display dims or goes black.

* Cellular radios enter a low-power state. The signal may weaken during this time.

* The camera flash is temporarily disabled.

* Performance slows with graphics-intensive or augmented-reality apps or features.

Additionally, if you're navigating, your device may show this alert and turn off the display: "Temperature: iPhone needs to cool down". Navigation still provides audible turn-by-turn directions. When approaching a turn, the display will illuminate to guide you through the turn.

Kind regards.