Hi H,
Could be a number of things, of course, but since it's affecting both of you that could be helpful. Presumably you have anti-virus something or other installed, but still the odd thing can slip through.
Have a look in Task Manager, (Right-clickthe bottom of the screen to find it) and see what resources are being used; at the bottom of the pop-up you will see CPU usage and memory usage. With the system idle there should be little or no usage.
Suggest you might like to download (if you haven't got it) Malwarebytes free, and run it from main screen: a full scan, which may take some time, particularly as the computer shows signs of being busy.... incidentally, have you had any other application (Word, Excel etc) slow appreciably?