We reported that there had been problems with the PS4, with customers complaining that it was switching off for no reason.
Sony said that problems were only affecting less than 0.4% of units shipped to date and they said in a statement: "This is within our expectations for a new product introduction, and the vast majority of PS4 feedback has been overwhelmingly positive." They added that they are "closely monitoring for additional reports, but we think these are isolated incidents".
So how do you fix the issues?
First off, check your TV compatibility or your HDMI connection. Some users have noted that, after initial problems, after updating the firmware on their televisions, issues concerning a lack of audio or video have been sorted. Also, it'd be worth checking the HDMI ports on both your television and PS4, as well as checking the cable you have.
If you think it might be the PS4 power supply, you need to switch off your PS4 completely, touch the power button on the front of the PS4 for at least 7 seconds until the system beeps twice, then disconnect the plug from the socket in the wall (you must only do this when the power indicator is turned off or you might corrupt data on your console). After that, try again. You can also try the power adapter from the PS3 if that doesn't work.
If you think it might be the PS4 hard drive, turn off the PS4 and press the power button for 7 seconds (again, until the system beeps twice) and disconnect the PS4 AC power cord from the electrical outlet. Then, when the system is completely off, detach all the other cables from your console. Then, slide the HDD bay cover in the direction of the arrow to remove it and have a look at the hard drive to make sure it is properly seated in the HDD bay. It is a pretty easy job to fix, but you are advised to check Sony's guide on that. If you're brave enough, you can install a new hard drive yourself.
If you think software is the problem, then try booting your PS4 in Safe Mode. Again, you press the button on your console for 7 seconds as above. There's more on that here. In Safe Mode, you can restart the system, update the system's software, restore default settings, rebuild the database (which scans the drive and creates a new database of all content) or 'Initialize PS4'. The latter loses all data and settings and returns your PS4 to the stage of being fresh out of the box. If you're doing that, read this first.
Sony have written a full guide to fixing your PS4 problems, and you can view it here.