I did a test on my site (only 37,000 questions but over 235,000 posts in total) and it appears that many queries are running when asking a question (I get 62). That sounds like too many for just asking a question so I'll check into it and see if there is some problem there.
UPDATE: if you wanted to check what queries are run on the ask action itself, you can. Turn debug mode on. In qa-include/pages/ask.php where you have the call to qa_redirect(...) (should be line 145 in v1.7), above that add the line
Now when you submit a question it will stop before redirect and show a blank page but with the debug info at the bottom and all the queries. Feel free to email me the list and I'll look for any bottlenecks.