Everything was fine until just this morning. I worked late last night and when I turned it on this morning, it made the noise, gave me the logo etc and turned on. However then suddenly went dark. I presume I must have run out of battery. So I charged it until the light went green. But whenever I press power it makes this tiny little click/vibrate and doesn't switch on. I've tried holding power and also holding shift control and option with power - it just clicks and doesn't turn on. This is a 3 month old macbook air 2015 bought recently and has been working fine. Having said this, the same thing happened once before for a while and then switched on later on. I don't remember what If anything I tried but it just worked. Any ideas?