Thats usual behavior for Ryzen 3xxx, whats important is load temp.
Go to BIOS and turn back everything to stock/default, download HWinfo 64 Portable (
https://www.hwinfo.com/download/) and Cinebench R20 (
https://www.maxon.net/en-us/products/cinebench-r20-overview/), close all other monitor software and run hwinfo 64 with "Sensors Only" option selected.
Once you have hwinfo on the screen, run CR20, and then click on RUN, when the rendering work start to show on the screen, then you should see all your 12 threads at 100% utilization. At that time, let it run almost till the end, and finally go see what temp does it show on hwinfo under the Ryzen 5 3600 tab on the sensor call: CPU (Tctl/Tdie) value.
Or you can wait till the test finish and just check the max column for that sensor -CPU (Tctl/Tdie) -
Also few important thign for Ryzen 3xxx:
- Use the lastest BIOS available.
- Download the latest chipset from AMD (https://www.amd.com/en/support/chipsets/amd-socket-am4/b450).
- Don't run motherboard software that you dont need (like MSI dragon center).
- Make sure you pick the Ryzen Balance power plan under the Windows energy settings (Win+R -> powercfg.cpl). In fact open the advanced tab of the Ryzen Balanced Power Plan and make sure the Minimum CPU State is at around 5% (sometimes it will show 90% and thats is not what you want). Max CPU State should be at 100% of course.
Finally, you may have 6 fans in your tower, but it does not mean that they are doing the right job. If you like to share a pic of your case internals where we can see the fans mounted it will be great.