Unusual Vertical Lines on my Xperia M

[RohitTech]

I bought Sony Xperia M a month ago. Phone is under warranty and I have its box and bill.

But since past 10 days I'm facing a weired issue.

Whenever I unlock my phone vertical colored lines appear on the display and disappear in some seconds. This doesnt happen on every unlock or occur daily but it happens on random days or unlocks.
Till now it has happened thrice.

I havent dropped the phone nor any similar incident has occurred.

Once unlocked, phone performs normally-- no hangs, reboots, call drops, no camera issues, performance or battery issues, colors too are displayed accurately etc.

What could be the problem or the reason for those lines?What can be done to resolve the issue?

[Hampus]

Hi and welcome to the community! Since you're new please be sure that you have checked out our Discussion guidelines.

Are you aware if you have done something special with the phone when this behaviour appear? For example, opened a specific application or similar? You can always try to boot your phone into safe mode to see if the same thing occurs:
http://talk.sonymobile.com/t5/FAQ/How-to-boot-your-phone-into-safe-mode/m-p/348008

[RohitTech]

No.

I always lock my phone only upon exiting all running applciations. Also I just use a popular messaging app and rest everything inbuilt apps.