I've just done a fresh install of El Capitan on my iMac. Erased the hard drive, fresh install..the whole shebang.Install went fine (or seemed too). I found early in the reloading stuff, and still going on, that when I just do "Restart from the menu", it will stall about half way thru the progress bar under the apple logo. It varies how far it gets, but it's about mid way. I'll let it sit for a few minutes, then force power off. If I then try to start it up, it will sometimes start just fine (and complain about being shut off because of a problem) or it will give me a grey screen with the mouse cursor (which will move) and the second monitor with the desktop bg. After letting that try for a few minutes, I'll power it off. Then it starts up just fine (and gives me the "hey, you shut off" message). So far, googling hasn't turned up any answers... any help?