I'm using Ubuntu 16.04 on a Dell Inspiron N5110. I'm also using a 9-cell battery, which Ubuntu calls "DELL YXVK215", in case that's significant. After installing some software updates yesterday, I'm having a few problems with the display and AC power. My questions are: are these problems related? Is it Ubuntu, hardware, or just a dying laptop? And what do I have to do to troubleshoot and solve them?
1. AC adapter not recognized
Sometimes, when the computer is on AC power, suddenly it will no longer recognize the AC adapter. It stops charging, and the green light on the AC adapter (which indicates that it's plugged in) shuts off. For a few minutes after that, the green light on the AC adapter won't work even if I unplug it and plug it in to the same outlet or a different outlet--the green light blinks for just a moment and then it shuts off again. After a few minutes, the AC adapter starts working again, but then sometimes it shuts off if I plug it into the computer.
2. Fan gets very loud and fast
Sometimes when the computer is on AC power, the fan gets very loud and fast. Unplugging from AC power slows the fan down again.
3. Computer shuts down with no warning
The computer keeps trying to shut down and restart itself. But in the middle of the restart process, it shuts itself down and restarts again. This happened a few times when plugged in, and a few times when not plugged in. It also happens when I'm trying to boot the Windows partition. EDIT: this is happening constantly now, so I can't use the laptop at all.
4. Screen resolution changes abruptly
Sometimes the screen resolution changes abruptly. Specifically, the screen resolution appears smaller (with black bars on the left and right sides of the screen, although the resolution in the "Display" settings is correct. Additionally, I'm able to toggle the "mirror displays" option even though I'm only using the laptop monitor. This happens whether I'm on AC power or battery power.
Sometimes all of the above problems happen at once, sometimes a few of them happen, and sometimes none of those happen. Everything's fine as I'm writing this, but I'm just waiting for it to happen again. I'm not even sure where to begin troubleshooting. I have the records from lshw and also the logs of the software updates, but I don't know what I should be looking at there.