Random PC Shutdowns- Software issue maybe?

[xLoveAC]

I have a DELL XPS 15 9550 4K screen.

I've been experiencing some random PC shutdowns, especially when I am playing Overwatch but it has occurred once during normal usage. What happens is I am playing and all of a sudden, the 'Shutting Down...' screen pops up and my PC turns off. This has been going on for about a week and never happened before.

This happens at seemingly random times as I started using a stopwatch to see how long it takes for this to happen and it doesn't occur at regular intervals (for instance, yesterday I played 8 hours straight with no shutdowns, but today played for 30 minutes and it shutdown).

Since the issue was getting progressively worse, I have reset my PC and now it occurs about once a day, but not more (as it used to occur several times a day).

 

All of my drivers are updated (I used driver booster to check for updates). I also checked for Windows Updates and DELL BIOS updates and everything is up to date.

However, I must point out that I haven't seen the "Updating, please do not turn off your computer" screen when you restart/shutdown/boot up your pc in a while which I don't know if it's an issue?

 

Power Settings:

- Fast startup turned off

- Hard disk turn off after: Never (plugged in)

- Processor use- 90% (plugged in)

 

Here are my specs during normal use:

 

I have run an sfc scannow and an mdsched.exe and no issues were found.

 

As for gaming, here are my max CPU temperatures while in the middle of an Overwatch game:

 

My GPU temperature whilst playing Overwatch reaches around 83C maximum, but is usually lower than 80C (sometimes doesn't go above 75C). I play the game with medium graphics quality, display-based FPS (caps at 70) and Vertical-Sync off (I know it is recommended for better use of CPU but it has response lag).

 

I have spoken to my brother who has been trying to help me (he studies Computer Science at university). We think it's a software issue rather than hardware, but have no idea what else to troubleshoot. Anyone have any idea what could be causing these random shutdowns?