Computer suddenly shut down not turning on

Hello,
Actually last night we were watching a movie & suddenly it got , shutdown we restarted it ,then it worked till welcome & again shutdown,,so I tried again to switch on the computer when I did it it showed some error & the last line was like some operating system not found ....idk what to do so today morning I tried to power on it again but it just light gets turned on & again off.....the Same is happening till now