Checkout Page Stuck (Load For Ages)

Hello, our website is CS cart 3.x ver, and it runs smooth.

But, sometimes when customer click the red button “SUBMIT MY ORDER”, Paypal checkout page is not appearing (Just stuck at checkout page loading forever)

I tried to clear cache and it didn't solve a problem. The problem is solved only when I clean reboot the server.

Any idea of solving this problem would be really appreciated.

Thank you.

Check your php error_log file for any signs of a problem. You might also look to see if there's an ajax response in your browser debugger or whether there is an error message instead of content.