Looping startup after downloading new OS X

I Downloaded OS X El Capitan last night. Things worked well. I shut down the computer for the night and this morning I tried start up. Start up looped by music, Apple on the screen, dark screen, shutting down and starting the process all over again. Tried safe start but it didn't work. I finally got to disk utilities and reloaded OS X. Tried restarting the computer and the same start up problems occurred. Any possible solution? Thanks!