The 500 error page is usually caused by bad permissions, a bad .htaccess file, or excessive resource usage.
To check if the 500 error is caused by the permissions on the file/folder, you will need to log into the cPanel and scroll down to the bar that says Files, and then click on the icon that says File Manager.
Once the page loads up with the folders and files, you will need to go to the directory where you are receiving the 500 error page.
Now that you have found the file/folder that is giving the 500 error, you will need to look to the far right of the file/folder to see the permission number of the files and folders. The default for files permission is 644 and folders 755. If the permissions are not the default and you did not change it yourself, it would be best to change it to the default permissions.
In the .htaccess file there will be some information depending on what type of builder that you are using to build your website. The best course of action for these type of cases is to create a copy of the .htaccess file with a different name and try to acquire a default .htaccess file from the builder that you are using to replace the current existing one.
In situations where the 500 error could be caused by exceeding the resources of the server, you have tools in the cPanel that will let you see the resource usage for the entire cPanel. On the right hand side of the cPanel there is a section that says STATISTICS that shows a bit of the usage.
To get more detailed information of the resource usage there is a bar in cPanel that says METRICS, and there are lots of useful icons there that can help you determine what is using up the resources.