I'm open to any thoughts.
Some random thoughts based on past troubleshooting episodes....
Trace one of your programs with Process Monitor and see if you can identify what calls the app is making during the 5-10 second freeze timeframe.
https://learn.microsoft.com/en-us/sysinternals/downloads/procmon
https://www.bing.com/search?q=how%20to%20troubleshoot%20with%20process%20monitor
Have you done any network throughput tests from the client to the DC's? Maybe test with dcdiag?
Standard response that I almost hate to suggest: turn off any antivirus software that you have installed.
Are you using a proxy to access the internet? Does the procmon trace show any internet calls? If you disable the NIC, do the programs launch any faster or produce any error messages?
Good luck.