black screen

LibreOffice quite often freezes, then goes into “not responding” mode, for no apparent reason. Recently, and more worryingly, when I’m typing in Writer, the screen goes black every so often, although my document spontaneously reappears after a few seconds, I’m glad to say. There is no discernible pattern to this occurrence, so far as I can work out. I tried uninstalling and re-installing LibreOffice, but the problem recurred. I tried starting it in Safe Mode, but again the problem recurred, leading me to believe that the problem does not lie with a corrupted profile. However, I thought it was worthwhile trying to reset my user profile anyway. However, although I tried to follow the instructions in the Resolving Corruption section of the Help pages, I just couldn’t find my profile. I went to Tools/Options/LibreOffice/Paths, then tried to find some of the items shown there in my C drive, but to no avail. I hoped that I might see something to do with LibreOffice labelled either “Profile” or “user”, but I couldn’t see either of these. So I just don’t know what to do, and expert suggestions would therefore be most welcome. Apologies if this question has already been answered, but I couldn’t see a solution in the database.