welcome to the forum,
much debated in the forum, that --backup-dir is not forever forward incremental backup
@for /f "tokens=2 delims==" %%I in ('wmic os get localdatetime /format:list') do set datetime=%%I
@set datetime=%datetime:~0,4%%datetime:~4,2%%datetime:~6,2%.%datetime:~8,2%%datetime:~10,2%%datetime:~12,2%
rclone sync c:/ z:/rclone/backup/c_drive --backup-dir=z:/rclone/incremental/c_drive/%datetime%
so, %datetime% = 20250130.120731
fwiw, if you are trying to sync the root of the c: drive, i would not use rclone.
what is the logic to backup folders such c:\program files, c:\windows
can exclude them using filters, such as --exclude and --exclude-from