I switched to using Edge browser, and the problems immediately disappeared. When I ran up task manager whilst using Chrome, I was seeing Chrome eating up lots of CPU (as high as 70% sometimes) even when I'm just sat there with a web page up and not doing anything other than looking at it. So I disabled the Kaspersky Protection extension and as soon as I did so, the CPU dropped down to around 1-2%. Turn it back on and the CPU starts to climb again and the problems return. I've been running the last couple of days with the extension turned off, and had no problems at all during that period.
Version is 188.8.131.528 (e) running on Windows 10. Chrome is Version 73.0.3683.103 (Official Build) (64-bit).
Best answer by Berny
> remove the Chrome extension > reboot
> reinstall (on top) Kaspersky > update databases > reboot