Inspiron 14 3000 display randomly turning off

I've had this laptop for a while now, an Inspiron 14 3000 with i5 8250U and Radeon 520. I use my laptop almost exclusively with the power adaptor and no battery. And I've had this problem for a long time, probably from the start, where my display would randomly turn off while I use the laptop, doesn't matter what I was using it for (browsing, Photoshop, etc).

When the display turns off, only the display powers down, I can still hear the laptop HDD and fan spinning. pressing caps lock on the keyboard also makes the caps lock button light up, so I don't think it's a Windows issue or a driver issue.

When this happened in the past, I could press the the power button to put the laptop to sleep, press it again and the display would turn back on, problem solved. I first suspect this is a power plan issue, so I set the display to never sleep (both on battery and power adaptor), but the problem still persisted. So I thought I just had to live with it.

But lately, the problem evolved, the display would blink black screens several times (black screen, display off, black screen, display off, and so on) and then it shuts off. Again, the HDD and fan is still spinning, caps lock button still works. But I can no longer turn the display back on by pressing the power button. The laptop goes to sleep when I press the power button once (HDD and fan stop spinning), and they both turn back on when I press it again, but the display stays off. The only way to fix this now, is to do a hard reset by holding the power button down.

Anybody can help me with my problem?