my iphone 6 sceen turns grey at random times .
i have had my phone for approxamitely 6 months and at random times the screen will fade out in a grey colour and my screen is unresponsive , this is a major problem because if anyone tries to contact me when this is happening I will not be able to answer. Also my apps turn inverted colours when this happens even though the setting for inverted colours is not on , please can somebody help me ??