These are fairly classic symptoms but they may not present obviously enough early on.
I had a power supply issue with my old Corsair CX430 (430 Watt).
The build had two old 95W Xeon CPUs, 2 USB devices and a PCI-E powered Nvidia Quadro or at one point a GT710. This shouldn't have overwhelmed the PS but this power supply is known to be weak by many users.
Symptom 1. Graphics Issues
This would only present it self after coming back with the........
sudo chmod 000 /etc/cron.daily/apt-compat
This is the easiest way to disable the cron without anything more invasive like deleting the file.
After that you won't have anymore apt-get's starting.
This can be critical for systems without much extra RAMthat is not in use. I've seen systems that have swapped and crashed over apt-get.........
For years I've always built cheap systems believing that there is little difference in more expensive components when it comes to reliability and quality, I generally believe this still except for Power Supplies.
I've always bought cheap cases with nice sounding 350-550W stock/cheap/crap power supplies and haven't had any issues for the most part until recently.
One such case is an NGEAR case with a 550W Optimax power supply, I always read that these supplies don't produce the........