Minecraft isint starting up

Hi there recently my minecraft has stopped working. One week before Christmas my I got im my computer and went on the minecraft launcher and pressed play it did its thing but when the launcher disapered minecraft never loaded I waited and waited and nothing happend so I restarted my computer and tried again, no luck, it did it till the day after Christmas when I resterted my computer it said minecraft was running and was blocking me from my computer from restarting so I canceled it and minecraft appeared, Its been working ever since untill today its doing it again! nothing is working please help.