ENVY laptop would not wake up, black screen with buzzing power cord. Removed cord and it did start

[LaurieAC]

Every evening I put my laptop in sleep mode by shutting the screen. In the morning, it "wakes up" when I open the laptop. This morning, however, it would not "wake up" and I got only a blank screen. I tried holding down the power button a few times and this did not work. I tried opening and closing it a few times and this did not wake it up, either. I could hear a buzzing sound near the power cord jack that would stop if I removed the power cord. There were no fan sounds. I could see the indicator light was on by the power cord jack and I could see some hint of white light under my power on button, but the button itself did not light up. I left the laptop for a few minutes and had the idea to try to turn it on with the power cord removed and it worked! It woke up, I saw the HP logo, and it is fine now. I was thinking that maybe the power cord was bad, but the laptop had about 75%-80% charge. I am afraid to close my laptop, not sure if there is something going on with "sleep mode" or if it is a failing power cord that caused this issue. Any thoughts? Please note, I am NOT tech savvy at all, so please state the solution in a simple, step by step manner, thanks!