How can I stop my monitor turning itself off and on again every few seconds

Install the correct drivers for the monitors.

It seems to be commonly overlooked that monitors often have drivers. 99.9% of the time monitors work fine with the "Generic PnP Monitor" that Windows provides and uses by default, but sometimes under specific circumstances it might not quite work perfectly.

It seems to be most common with monitors that have aggressive power saving modes.

Dell monitors seem particularly sensitive to this. Here is the list of Dell monitor drivers. You can find your monitor model either printed on the back, or often by bringing up the on screen menu. If you don't have a Dell monitor, check your manufactures website for drivers/support.

1. Download the driver.

If the driver comes with it's own installer, just run that and everything should be done for you. If it just comes as a zip file, then you will need to follow these remaining steps to install the driver.

2. Unzip the driver.
3. Open device manager.
4. Right click on the monitor.
5. Click "Update driver software".
6. Select "Browse my computer for driver software".
7. Find the location you unzipped the drivers to.
8. Click next to install the driver. You should get confirmation that the driver was updated.