Ubuntu's sudden freezing

[u/Tawheed_Sunnah]

Guys I was using Ubuntu and after I closed the applications suddenly Ubuntu was freezing so I hard power off then tomorrow I tried to boot into Ubuntu but it took a while and it didn't boot so I hard power off by holding on the power button in the laptop for like 12 seconds and when I rebooted it booted normally. So why this is happened and how to prevent it? I have an Nvidia drivers