Weird, freeze, crash now grey screen- help please

This morning my kid was working on an online advent calendar when the screen went a funny blue and froze, then started clicking- like an old movie reel on the projector. I did a forced shut down but now when I power up I get the apple icon on a grey screen with a status bar that progresses slowly and also seems misaligned at the right side of it.

Then the status bar disappears and the computer either shuts down or screen goes completed grey...cannot do anything

It is a Mac Book Pro early 2011 with El Capitan installed.

Any help is very much appreciated