Several months ago, I read an article in Consumer Reports that touted
AVG antivirus as the best antivirus app for Mac. Consequently, I downloaded and installed the free version. In retrospect, I should have suspected it when I experienced slowdowns in my computer, including apps that were slow to load and some wonky behavior. AVG kept nagging me about upgrading to the paid version (which I ignored) and gave frequent popup messages that tried to scare me by claiming that something was amiss (in truth, after the first attempt at using it to scan my drive, I hadn't opened it). Then, my wife complained that the computer was frozen. I had to do a forced shutdown and immediately went into Console to consult the crash log.
The crash log showed that AVG was the culprit. I uninstalled AVG by using its uninstall feature in its application menu and then searched for leftovers with Spotlight, Easy Find, and Find Any File. Interestingly, Spotlight found very little compared with the others, and I trashed all the detritus. Since then, my computer is back to normal, no issues, no freezes, and apps launch speedily.
Bottom line: AVG is a virus unto itself. I haven't experienced anything like this since Norton Antivirus caused kernel panics, back in the day. DO NOT USE THIS APP!