My Macbook Pro Retina (13", Late 2013) doesn't always power on properly, what is the issue?

Hi,

Lately, my Macbook Pro Retina 13" Late 2013 with OS X Yosemite 10.10.5 gives intermittent problems during turning on the mac and behaves weird especially around the power button.

Here are the problems I face:

1) When I am working and accidentally if I touch the power button, my mac turns off display and doesn't respond at all. I tried to press the power button and it still doesn't respond even when my mac is 100% charged. Basically pressing the power button doesn't work.

2) After some workaround, I found that the only way it powers on again is by following this procedure: Press and hold the Power button for upto 10 seconds. Whilst holding the power button, connect the MagSafe charge to Mac and continue holding the power button for another 10 seconds and then release the power button. Press the power button once and then it boots properly. After it completes the boot sequence, the macbook works just fine.

3) However when it goes to sleep then again the same problem. It doesn't wake up at all. I have to carry out Step 2 again and its frustrating.

Addiitonal info: I have tried SMC reset, PRAM/NVRAM reset, the colour on MagSafe changes from orange to green as mentioned in the Apple's Resetting SMC guide, but the power on problem remains. When Macbook is on, everything works as normal as it should. The battery charges properly and there is no other issue.

Can someone help please?