First, let's be clear on the terminology. I'll assume you're using it correctly, but often that's not the case with new users, and I don't have a clue about your experience level, which might very well be "higher" than mine. So, I'm assuming that you really are talking about the Desktop, aka the "background", or the "opening screen" when only Finder is running, and not a Finder Window, which would require opening a folder or drive.
Given that, I'd suspect a defect in the Desktop plist file, found here:
To test that theory, move the indicated .plist file to the Desktop.
Restart. This will create a factory default plist for the Desktop.
Now I guess you'll have to use the computer awhile, hopefully a long while, to see if the problem persists.
If it doesn't, then you can Trash that .plist file you placed on the Desktop.
The only reason to keep the relocated .plist file around is in case you want to put it back. You'd want to do that to save yourself the "trouble" of redoing any preferences you had changed for the Desktop. So, if the problem does persist, you can really choose either plist file to keep, and get rid of the extra one.
The next step I'd advise would be to log in under a different User Account and see if it has the same symptoms.
Every now and again, the View options on my desktop change - the icon size reduces, grid spacing goes to maximum and the Arrange By setting goes from snap to grid to name. It can take some time to re-arrange everything.
I can't tie it into any particular activity or action. I don't run a lot of applications - I use MS Word and Panorama (database management software) every day but the problem doesn't arise every day. Any ideas why this might happen?