Sounds like your virus scanner. The first time you start PP, the scanner goes through all the Jar-files to check if they happened to become a virus while the computer was switched off. The second time the program is started, the scanner at least remembers that the check has been done and because it’s impossible that jar-files are changed while a computer is running, the scan of these jars is skipped.
If you’ve sensed sarcasm, congratulation 