macbook air shuts down intermittently, boots at its will when power pressed,sometimes doesnt.

I have a macbook air 13" mid 2014 model purchased in india on 29th june 2014.(sadly the warranty is just over by a few days)

I remember getting this issue after installing 10.10.4 update.

before that everything worked well.

THE PROBLEM:

the mba shuts itself randomly, anytime it wants, even when its just booted up.

I put it to sleep and in most cases when i see next morning it is shut off. The battery is charged nearly full, then also this happens, irrespective of power cable attached or not.

When trying to restart, it sometimes just doesn't respond. Its like power button just doesn't work at all.

and when it feels the mood to turn on, it turns on after many presses of power button or trying after some time. and then again shuts off when it wants.

Please guide me .

I am a student and bought it from my pocket money, and dont have enough to pay for the repairs and didn't had enough to extend the warranty either.

Please tellme what I am dealing with here?

Is it just a nominal software issue or a grave hw issue?

have turned the device in to apple service center. He said to call in 1-2 days. and I am panicking here.

Any help would be greatly appreciated.

Thank you.