Suffering occasional system freezes

[Moltke]

Hi [member=7114]ian_r_h[/member]

Being new to Linux, I was wondering if anyone has any advice on how to go about diagnosing such freezes - for example, which log files to check, what terminal commands to try, etc.?

Since there might be a number of reasons for that to happen, it's really hard to tell/advice about how to proceed without being in front of that pc. However, there's plenty of info on google and running a search with the right terms should be the first step, I know, easier said than done, cause sometimes those "right terms" are not that clear to us specially when we're not sure on what we're looking for. In your case I googled for "ubuntu freezes" and "view logs in linux",  this brought up some interesting results. Read and see if you find something that may help with your issue
https://askubuntu.com/questions/4408/wha...tu-freezes
https://askubuntu.com/questions/761706/u...g-randomly
https://askubuntu.com/questions/916966/h...em-freezes
https://unix.stackexchange.com/questions...ntu-system
https://www.maketecheasier.com/4-ways-to...ntu-crash/
https://bugs.launchpad.net/ubuntu/+sourc...ug/1677491
https://ubuntu-mate.community/t/screen-f...nsive/5610
https://www.linux.com/learn/sysadmin/vie...mmand-line
https://www.cyberciti.biz/faq/linux-log-...ogs-files/
http://www.thegeekstuff.com/2011/08/linu...log-files/

It's a lot of reading I know but I'm sure not only you'll learn quite a few interesting things but also find something helpful in any of those articles/posts that will help you in diagnosing/resolving your issue, so next time you might tell us what to do when facing a similar situation

Hope this helps!