I have iphone 4 in 4.2.1 two weeks. Yesterday when i put my iphone in my pocket somebody called me ( i didnt understand it, i learnt it afterwards) and when i looked at the phone it wasnt responting in anything. I did hard reset to open. It happened two times yesterday and one time today. And all three times when i put it in my pocket. Its not jailbroken! Help me plz.