Can anything change in a computer without the user modifying something
Yes, definitely. Most obvious example: the clock, it changes all the time!
Other examples of environmental factors that change without the user actively manipulating them, are temperature and humidity. Temperature influences the workings of electronics heavily, and humidity has an influence on the behavior of electrical connections. Another external factor that is only partially under the user's control is the quality of the mains power.
Modern high-performance CPUs and maybe even more so GPUs, to a lesser extent also RAM, are built right at the edges of what is possible given our current understanding of physics and our current level of engineering. Some might even argue that the really highest-performance CPUs and GPUs may already be over that edge.
Even the tiniest fluctuations in mains power can, at least with a badly designed power supply, have devastating effects on the stability of the electronic components. Modern CPUs can manage their frequency themselves, based on power and temperature, and may run at different speeds given the ambient temperature, which may in turn lead to some timers being off by a tiny amount, which can lead to an overflow happening or not happening at the right or wrong time.
The possibilities are endless.
There is also another possible explanation that is admittedly rather "out there" (literally): cosmic rays. While the probability that a cosmic ray will hit exactly one transistor in exactly your computer's RAM in exactly the right way to make exactly the most important bit flip from 0 to 1 and crash your computer, is extremely tiny, there is also an extremely large amount of computing devices in the world. If you're a sysadmin at Google, for example, you'll probably see it happen more often than you will see a car accident on your way to work.
There could also be a rather benign explanation: a counter.
For example, one of the devices my employer makes, has three copies of the OS installed in three separate partitions: user 0, user 1, and recovery. On boot up, there is a counter that is incremented, once the boot has finished, the counter is reset to 0. Once the counter hits 3, the boot sequence switches to the other user partition. If the counter hits 3 again, the boot sequence switches to the recovery partition, which has an older, more stable, stripped down copy of the OS, and attempts a self-repair. The device also calibrates its RAM during boot up, but not during runtime. So, if the temperature changes drastically between boot up and runtime, the calibration may be off, something may crash, which causes the watchdog to reboot the device, which causes a recalibration to different values.