My BPB 15" is about 4 years old as well and this morning I experienced this for the first time. I closed the lid and put the MBP in my bag and went to a quick meeting (about 45 minutes total) and when I took the MBP out of the bag it was making noise (fan was running) and was pretty warm to the touch. I think I had closed all programs prior to closing the lid. I manually powered the MBP down and then restarted and it is fin, but of course the battery is very low after just 45 minutes. The fan never funs when I am using the MBP so this noise was new to me.
My concern is that in 2017, after 4 years and how many updates Apple has had, why did this happen all of a sudden? Is there anyone that can help me understand what this happens? I see the string for this topic is 5 years old so I assumed the issues were gone.
Thank you for any assistance on this. Heck maybe it will just never happen again.