Since none of us are mind readers, bsdnewbie, all we can do guess.
If you want us to guess:
- FAQ 8.22 might apply.
- You may have insufficient RAM
- Your video configuration might be a problem
- You may have a failing disk drive causing read retries, delaying I/O.
If you don't like these guesses, please follow the advice in
www.openbsd.org/report.html, under "How to create a problem report".