Will not boot from internal drive + fog on internal display glass

Heya folks! Normally, I wouldn’t be asking for a question, but I need help.

So this old Mac won’t startup from the internal disk. It just loads and loads and loads… and so on. There’s no recovery partition on the internal HDD, and after waiting for about 30 minutes, I shut it down, because some weird fog was forming between the LCD and the glass.

Any ideas? I’m so clueless when it comes to EFI and Macs.