With Windows performance quirks, always check you do not have antivirus software running. That's a leading cause of slow load times. Make sure all A/V software is fully disabled or uninstalled, including Microsoft Defender.
With Pro Tools 12.5 Ultimate you should likely be running with disk cache (set to cache the session) so disk performance etc. hopefully wont' matter. And besides slow disk does not
Another leading suspect that might cause this is memory exhaustion if Windows is having to page out stuff to make room in memory. Make sure no background programs are running, no web browsers, etc. and you've already uninstalled Avid Link and Cloud Collaboration bloatware). Look at memory activity. See
https://www.techrepublic.com/article...k-memory-usage (and as pointed out there do not worry about "free memory" it's a largely useless metric).