Cursor suddenly tabs through text and apps

Hi,

I am having an issue. Not sure whether it's my keyboard or my mouse but the cursor suddenly moves on it's own.

When searching in Finder it tabs through the app selection. If I'm correcting text it will skip forward to the next character until there's nothing left in the text to tab through. It happens occasionally.

Anyone else had the problem? It stops when I take the batteries out of the keyboard or if i disconnect my mouse.