How to determine the cause of Ubuntu freezing?

Question

linux

Sometimes, about once a week, the working desktop Ubuntu hangs or starts to slow down wildly. This usually occurs when running heavy applications, but not always. Application windows stop responding to mouse and keyboard actions, or react with horrendous brakes.
But at the same time, you can easily switch to terminal mode by CTRL+SHIFT+F1. At the same time, the processor turns out to be almost free, there is also a lot of free memory. When I return to graphical mode, nothing works normally. Have to reboot. I encountered similar problems on computers with different configurations, so I can’t attribute this to crooked iron.
Trying to kill from the terminal in turn all the processes I started does not change anything.
How to find the reason? What to watch? Where to dig?

Answer 1

logi
/var/log
syslog.log
messages.log
...