HI Hello
You can |dentify your problem by doing following steps:
1. start your computer press f10 and keep remain power on if there is no shut down issue with oprating system
2. if your system start and after some time it shut down .you again power on the system but this time it shut down less time.I think this issue with power supply as your system is completely shut down not restarting.
3
try run below digonstic tool to find out more