I'm American military living in South Korea and I have not been able to find a good answer after several hours of searching with this question. I have no background or formal education with circuits and therefore my understanding of most items on this topic is fair at best. I've been in my off-base apartment for 2 weeks with no problems. About 3 days ago, my laptop started to slightly vibrate when plugged in. When I closed the lid and put it in hibernate, it would not vibrate anymore. Then a few days later it would vibrate when hibernating. I use the transformers provided with my apartment which is 2 prongs and brings down the 220v to 110v and I have a 3-pronged powerstrip plugged into the transformer, which I then plug in my 3-pronged laptop power cable. I tried different outlets and different transformers in my apartment with the same result. I brought my laptop on base with the US standard electricity and the vibration did not occur. So from this, I also know it's not my laptop charging cable. From searching online, many posts said it is likely a grounding issue. Any input given would be greatly appreciated. Thank you.