Laptop is turning off AND on randomly - Possible power button issue

[UltimateZer0]

My Samsung laptop (specs at the end of this post) is turning on and off on its own. By that I mean it simulates force-shutdown while I'm playing a game, watching a video, browsing, typing a post (just like it did now), coding, or while it's simply idle. It sometimes turns on again after a random interval, and sometimes it enters what I call "hiccup mode", where it keeps restarting at Samsung logo before booting anything, or while loading Windows, or even after loading Windows.

Here's what I've tried and made no effect:
1- Changed the thermal paste and made sure the laptop doesn't overheat (This slightly affects the occurrence of the problem).
2- Alternated between running it on battery only and power cable only.
3- Booted from a USB driver (Set USB drive as the highest boot priority).
4- Kindly asked the laptop not to do that.

From my trials, I concluded that it's not an overheat issue, a software/OS issue, a hard disk issue (HDD Sentinel reports EXCELLENT status), battery/power cable issue, a network issue (It happens whether I'm connected to a network or not), nor a demon possession issue. Also, I'm running it on power saving mode with only 10% allowed CPU usage.
Sometimes it works perfectly for weeks, sometimes it can't stay on for 5 minutes.

Now, I noticed something that kinda narrowed down the possibilities of the problem.

If I have my power button set to "Sleep" when I press it, when the problem triggers, it appears like my computer is going into sleep mode. Sometimes it simply does, and sometimes it force-shutdown while doing it (it's like someone pressed the power button once, then pressed and held it, which led to force-shutdown). And similar process happens if I set the power button to "Hibernate" or "Shutdown".
If I have it set to "Do nothing", it only force-shutdown when it happens.

I'm not much of a hardware expert, but I think it's like the power button circuit is receiving signals when it's not supposed to, acting up weirdly.

What could possibly be the issue?

Here are my specs:

Model: Samsung NP300V5A-S06SA
CPU: Intel Core i7-2670QM
Graphics cards: built-in Intel one, and NVidia GT 520MX
HDD: 500 GB
RAM: 6 GB
Usage: 2 years, very heavy usage (carry it in a backpack outdoors sometimes)
Other irrelevant issues: a vertical white line across the screen (dead pixels).

Thanks in advance for any help.

 

[Rit_86]

Follow these steps
Remove the battery and the AC adapter from the laptop.
Press and hold the power button for 30 seconds and release it.
Reconnect the battery, AC adapter and switch the laptop on.
See if it helps.

 

[UltimateZer0]

Follow these steps
Remove the battery and the AC adapter from the laptop.
Press and hold the power button for 30 seconds and release it.
Reconnect the battery, AC adapter and switch the laptop on.
See if it helps.

I've tried it. I see no effect yet.
Was this meant to discharge something?

 

[Rit_86]

Yes, it was meant to discharge any static charge that may have accumulated on the power button.
If it didn't help, it's better to give it for servicing. It seems your guess about the faulty power button was right.
If the problem persists even after replacing / repairing the button, send it to an exorcist. I think there may be a demon inside it after all

 

[UltimateZer0]

Yes, it was meant to discharge any static charge that may have accumulated on the power button.
If it didn't help, it's better to give it for servicing. It seems your guess about the faulty power button was right.
If the problem persists even after replacing / repairing the button, send it to an exorcist. I think there may be a demon inside it after all

Thanks, it's currently up. I'll keep using it (will watch a movie or two, play a game) and if it shut down again, I will update this post.
I gave it to a repairman before and he was convinced that it's an overheat issue (even though I told him all the details), and he changed the thermal paste and cleaned it up a bit. It worked fine for one day, then it started happening again.