When I go to Edit/Preferences/General/ and then make changes .e.g untick show splash screen, and untick show dialog when memory card is inserted. If I close LR and then restart, my changes in Preferences have now been restored, Splash screen appears and all previously unticked boxes are now ticked again.
Reset the preferences file. This is Adobe speak for deleting the preference file, then letting LrC recreate it. Note that some settings may return to defaults, you will need to change them, then test. The preference file can get corrupted leading to buggy behavior.