4GB Ram does not cut it with W10.
I was having the same issue with my laptop and last week threw in the towel, bumped the 4Gb up to 12Gb and replaced the HDD with a SSD , like owning a new PC.....
I concur, my W10 ran fine with 4gb Ram, so did the one upstairs, but as I added more software and the more regular the updates from W10 , the slower the machine, it became frustrating with excel, windows, spotify and thunderbird open and then sitting watching the blue circle rotate.
I have been using my upgrade machine now for the past couple of days and cannot believe that I endured more than a year of frustration, should have done the upgrade months ago....