contig.exe code at boot time

Good day.

I understand that Sysinternals' Contig program can defragment the $Mft file as follows:

contig.exe c:\$mft

However, I was wondering if one of you could share the (hopefully) few lines of code that will make this command run at boot time before Windows is loaded. Than you for your attention.

No Windows program can run before Windows is loaded.
You probably need a bootable USB drive containing a Windows PE or RE environment, with a suitable utility on it to do the defrag.