Sims 4 Crashing PC, no mods

@beefpetunia  Sorry for the late reply.  I went over the log multiple times and couldn't find anything that looked even remotely problematic.  The power on all rails is above the requirements, the temperatures of all components (that report it) are low, and there's no other weirdness.

The one thing I didn't see was a report from the graphics card about the voltage coming in from the power supply.  This could simply be a lack of related sensors on the GPU, or that hwinfo isn't reading the sensors properly.  But it did make me wonder: is it possible that the 8-pin supplementary connector has become detached or was never present in the first place?  Please check if you're not absolutely sure.  Not only should there be a cable from the PSU to the GPU, all eight pins should be inserted rather than 6.  (Many PCIe power cables come in a 6+2 format for wider compatibility.)  And it's easy for this connector to come loose because the cable is often bent downwards very close to the connector.

If that's not the problem, I do have one other suggestion that may or may not help.  Install RivaTuner Statistics Server (it's a free download) and limit the framerates in Sims 4 to 30.  You should be able to play with much higher fps, but this is more of a test than a solution.  The RTSS menu will look something like this:

You'd choose TS4_x64.exe (below TS3W on the left), set the framerate limit (red box) to 30, and choose whether to start RTSS with Windows (yellow box).  You don't need to do this, but RTSS does need to be running in order to work.  Restart your computer after installing RTSS and before trying to play.

If a limit of 30 works, you can try 60 next, then work your way back up to 144 (the refresh rate of your monitor) and see how it goes.  RTSS shouldn't affect any program for which you don't specify an fps limit.

Hi thanks again for all of your suggestions and help, I really appreciate it. 

So, I checked the 8-pin supplementary connector, it seemed perfectly fine to me but I gave it an extra push to be sure it was in correctly. I loaded the sims and it actually worked! However, when I went to log on later that night, it crashed the computer again. 

I also tried the RivaTuner Statistics Server with 30 frames as you suggested and the game loaded fine until it hit the main menu screen, which is when it crashed again. From all of this it seems like the PSU might be the problem? Let me know what you think. And again thank you for your continued help.

@beefpetunia  If you have the ability to test with a different PSU, even if it means borrowing one from another computer or a friend, I would suggest doing so.  A 500W unit should be fine, but if possible, go with 600W or above just to be on the safe side.  You don't need to install it properly; just leave it on the desk and hook up all the connectors with the computer's side panel removed.  And, as noted earlier, make sure the PSU's fan is pointed towards fresh air, not against a solid surface.