Major computer issue please help

My Samsung pc is being super weird right now. I always shut it down when I’m not using it to be “efficient” but today when I restarted it, the Dell screen popped up and was loading. But there was little text at the bottom saying “diagnosing your pc”. I was like what??? After that it came to this blue page that said “problem booting your pc” or something like that. And it gave me the option to restart it again or do other technical stuff that idek about. The pc is kinda old, like 6-7 years. But it’s worked PERFECTLY in the past and this is the first time I’ve ever seen this. My dad used to fix computers so he tried EVERY THING and he still can’t fugure it out. I play the Sims 4 and I’ve downloaded custom content and kids for my game but I’ve never had a problem with that. My dad said that there could be a problem with the hard drive. But idk. I’ve never seen anything like it so I really am clueless. Anyone know any solutions or advice or whatever?? As long as you can help that’d be great!!! Thanks!