Hi,
Wondering if there was a problem with the fan, as it is the only moving part in the laptop, unless the buzzing sounds more electrical then mechanical.
If the fan fails intermittently then the laptop may begin to overheat and it will be shutdown to protect the CPU.
I suggest that initially you ''back up your data'' to an external storage drive while the laptop is still working as you may have to open it to get to the storage drive to retrieve your data if the motherboard fails some time soon in the future and it is not that easy with this laptop.
Here’s the ifixit [guide|127330] guide that may give you some idea of what’s involved. This is not a repair guide but at least it shows how to access the various components.
If doing this seems too daunting, contact a reputable, professional laptop repair service and ask for a quote to repair the laptop