Ubuntu freezes randomly with audio playing in the background

BIOS

Dell Precision Tower 5810

You have a very old BIOS, A14.

There's a newer BIOS available, A33, dated May 4, 2020, and can be downloaded from here.

Note: Verify that I've got the correct web page for your model #.

Note: Have good backups before updating the BIOS.

/swapfile

Let's increase your /swapfile from 2G to 4G.

Note: Incorrect use of the rm and dd commands can cause data loss. Suggest copy/paste.

In the terminal...

sudo swapoff -a           # turn off swap
sudo rm -i /swapfile      # remove old /swapfile

sudo dd if=/dev/zero of=/swapfile bs=1M count=4096

sudo chmod 600 /swapfile  # set proper file protections
sudo mkswap /swapfile     # init /swapfile
sudo swapon /swapfile     # turn on swap
free -h                   # confirm 16G RAM and 4G swap

Edit /etc/fstab, using sudo -H gedit /etc/fstab or sudo pico /etc/fstab.

Confirm this /swapfile line in /etc/fstab... and confirm no other “swap” lines... use SPACES in this line... confirm NO TABS...

/swapfile  none  swap  sw  0  0

reboot                    # reboot and verify operation

Reinstalling the operating system does not fix the freezing problem seems to indicate that your computer has a hardware issue. The freezing video with audio still playing in the background is characteristic of a graphics processor problem. The Dell Precision Tower 5810 has an AMD FirePro W4100 graphics card. The graphics card may be faulty due to a lot of hard use or it may be malfunctioning due to overheating because the computer is overheating very quickly, but the usual culprit in situations like this one is the graphics card. Fortunately a discrete graphics card is easy to replace.

Overheating could be caused by:

1. Dust and debris blocking the openings between the fins of the aluminum heat sink on the CPU.

2. A worn out out fan.

3. Cracked or otherwise worn out thermal paste between the CPU and the aluminum heat sink on the CPU.

If the CPU fan needs to be replaced, it may make sense to replace the CPU fan together with the aluminum cooling block as a single assembled unit, if the two parts are sold together as a single assembled unit, and solve all three problems at the same time.

While you're waiting to decide what to do about your computer's video freezing problem, you should install the Psensor (psensor) graphical temperature monitor application from the default Ubuntu repositories in order to provide real-time information about your computer's CPU and GPU temperatures. The Psensor icon is located in the notification area in the upper-right corner of the desktop. The Psensor icon looks like a little thermometer which you can click to show the fan speeds and the CPU & GPU temperatures. If the speed of a fan is slower than normal and that fan is spinning all the time, this is a good indication that the fan is starting to wear out due to friction on the bearings.

XSensors (xsensors) is another graphical temperature monitor application from the default Ubuntu repositories repositories. XSensors is similar to Psensor, but it has additional features and a more elaborate graphical user interface.