Automatically downloaded /and installed/? Did you restore anything after the reset? Can you see what is installing then (Play Store will tell you if it is doing it)? And what apps?
Have you made any changes, e.g. using some app to root it? Have you installed apps from sources other than the Play Store?
A lot of questions, but trying to work out whether you may have picked up some malware that has infected your system (which will make it immune to a reset), or installed and restored an app that's doing this (or otherwise reinfected after the reset). The way to fix an infected system is to reflash the device completely with a new set of software (I don't know procedure for an LG), but that won't help if the cause is something that you think is innocent and reinstall, hence other questions.