Window10 'START MENU' wont open.Get message'Start Menu isn't working...HELP !

[Windows Central Question]

Window's 10 downloaded Nov 2015..on HP 4 year old Desktop..'compatible with Windows 10. When Click on START MENU message comes up"START MENU isn't working. We'll try to fix it the next time you sign in" I close down, sign off try again...still doesn't work. Now & then it does but seldom. HELP!