Loose or bad usb cable . Maybe keyboard or mouse . My pc started randomly doing this every time I got out of or moved my chair . Drove me nuts for a while . Now I am trying to prove my latest theory . I creat a static discharge when slidilng out of my chair that would trigger the usb to reset but not be logged . Took over 2 years to track this odd one down th this theory . Only happened on low humidity days and then only a few times a day and only a few days a month . Drove me bonkers enough to log it and stick to finding the cause . Have not recorded enough data need more time data points for definitive proof but replacing mouse , or the act thereof , stoped the symptoms for close to a year before it started again . It will probably take me a couple of more years to quantify my data , as it just started again last week .