Welcome to the Lightroom Community. I'll need more info to help you figure this out. I've checked your account but could not find any crash reports. If your entire machine crashes, the issue could be broader than Lightroom Classic. Open Event Viewer from Windows Search.
- Go to Windows Logs > Application Logs & look for Error & Warning logs.
- Share the log related to the Lightroom Classic crash instance with us.
To test Lightroom Classic, pause the sync right at launch & then monitor the task manager & the event logs.
Try booting the Windows OS in safe mode to skip loading third-party programs & other factors that can cause such issues.
There could be a broad list of reasons unrelated to Lightroom Classic for such behavior. We need to know more.