Finder window keep opening

Hi,

I did search for solution through Google and this communities but I see many of them are old. For a couple of times, the Finder window would open up by itself and a couple of times, the Finder windows would open like 12 windows overnight. I am very new to Mac. I found this link but only did the part where "Safe Finder adware manual removal for Mac" and "Get rid of search.safefinder.com redirect virus in web browser on Mac" is. The rest seems so complicated and I do not want to download their product. I recently downloaded "Avast" antivirus hoping it is better than what I already have, the "Webroot" antivirus but both of them did not detect any viruses. Any help?