After the freeze can you start the game right up again okay? Or do you have to reboot, or wait a while, before it will run again?
DXDIAG is a program you run from the Windows search box on the task bar. After running it will open a window and start collecting info with a progress bar in the lower-left corner. When it completes click the 'save all information' button and save it to a file then attach that file here.
Please attach your Documents/Paradox Interactive/Stellaris/settings.txt and pdx_settings.txt .
From your Documents/Paradox Interactive/Stellaris/logs/ folder, attach system.log , error.log .
Please report the temperatures of your CPU and video (GPU)
1/ before starting the game up and
2/ after say 10 minutes' play.
If your PC's vendor has given you no way of reading temperatures, install