By default, your iPhone screen lights up when you receive a new notification, such as a text message. If your iPhone screen lights up periodically otherwise, the device may have operating system or hardware issues. Different applications can also affect the handset's notifications.
If you own a new iPhone device and the screen lights up without a notification, the problem could come from faulty parts or poor manufacturing and the device may need service. If the problem occurs on an older iPhone, you may be able to solve the problem by cleaning the hardware. Over time the docking port can accumulate dust and small bits of debris, which can interfere with the charging process, causing the notification light to come on during charging. Use a cleaner formulated for electronics to clean the docking port, and the outside of the device itself.
The OS controls your iPhone's various functions, including notification lights and the screen itself. Glitches within the OS can cause your phone to light up without first receiving a notification. These problems can result from a bug within the operating system, or from a user-generated problem such as may be caused by jailbreaking. Resetting the OS to the factory defaults may correct the problem. To reset your iPhone, press and hold both the "Sleep" and "Hold" buttons simultaneously for 10 seconds. Release both buttons when the Apple logo appears on the screen.
Many applications, such as news, weather and social networking apps, periodically scan for updates and send notifications to your iPhone. As a result your iPhone screen will light frequently, depending on the individual app. Check the settings menus on your apps and turn off the notifications. If the problem still occurs, remove the app entirely.
Apple offers a limited warranty for iPhones. For example, the iPhone 4 has a one-year warranty from the date of purchase. This warranty covers any problems caused by manufacturing or the parts used. Apple may also repair or replace your iPhone for a fee if you have extended the warranty time or do not qualify for the warranty. Visit Apple's Service and Repair site to get specific information on your device.