Hi David and Michael,
I was just about to create a post on this issue, as I've been also experiencing delays while opening Mission Planner. Both the frequency and duration of the delays appears to be random in nature. I was hoping I'd be able to provide a log of this behaviour from this morning, but of course the program opened without any delays. The next time I encounter the issue, I'll be sure to post the log right away.
David, if you navigate to C:\ProgramData\Mission Planner, you should see a number of time stamped logs. Make sure View > Hidden Items is checked.
In case my system information is relevant, I am encountering this problem on a brand new installation of Windows 10 that has been fully updated.