Trash fills and empties by itself

I tend to keep my Trash empty. But as I use my Mac I occasionally notice that the Trash icon changes to full trash, and then immediately back to empty trash. - This happens in a second. I have noticed this behaviour several times over the past few months at different times of the day. It also seems unrelated to what I am doing.

I am concerned that the security of my mac may be compromised or that there is spy/malware present. Could this be the case?