Since installing El Capitan, I have noticed on a few occasions that when I wake my iMac from sleep and begin to type my password into the log in window, the keyboard begins to populate the password field on its own. Its as though the keyboard keys are being held down, but isn't. No matter how many tries I have to delete, I always end up powering off my iMac and restarting. Once its restarted its fine. It can then go from working fine, to doing the same again. Anyone else experienced this or have any idea what it could be?