Touch not working problem

ZF Model: ZE554KL
RAM: 1G
Firmware/APP Version: Zenphone Mobile
Frequency of Occurrence: 10
Rooted: No
APP Name: Zenphone mobile

Suddenly and frequently for long time touch is not working. when by Switching it OFF by long press of power button also, it remains the same. When got struck with touch problem, it remains with problem a day/ 6hours/ 3hours. To make it work, have to wait and suddenly by fluke it starts after a period. Its been big head ah and not able to depend on this mobile. Don't know what is the problem.
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