Question PC screen going black, with noise from PC

Nov 8, 2020
Thank you in advance for your help. I am new to the forums so if there is a better place for me to post this question please let me know!
I bought a "gaming" PC in August of 2019. For the most part it has ran every game I've tried quite well. About 5 months ago, it started developing a problem. At first, the screen would freeze for a second and the PC would make a quick noise, and then things would return to normal. It continued like this until recently. Recently the screen has been freezing the same as before, but then going black, with the same noise coming from the PC. The screen then comes back on after 5-10 seconds. This seems to be steadily worsening - becoming more frequent, and lasting longer. Unfortunately I don't know how to describe the specific noise it makes, other than it sort of sounds like the PC is grunting.
Here is the PC, if I miss any important parts let me know:
Intel i5-9400F 2.90 GHz
NVIDIA GeForce GTX 1660
16 GB DDR4
1TB HDD (800GB free)
220 GB SSD (50GB free)
Windows 10
PSU - Thermaltake SP-600AH2NKW
One last thing - I was trying to solve this problem myself a couple of weeks ago, and downloaded some system monitoring software that revealed my CPU was running at 99 C, who knows for how long. It turned out to be a problem with the way the thermal paste was applied, and has since been fixed. CPU temps are now around 55-60 C while gaming. The problem the PC is having has continued unchanged since this fix.
Based on this information, what do you think my problem is?