You could turn on profiler or, better still, extended events to capture the query executions that are occurring. But, there's a way to look at what was going on at the time on the server using SQL Monitor. On the main screen, in the upper right, is a clock. You can click on that to rewind time. You can go back to the moment when the problem is occurring and then look at the longest running queries or the queries using the most resources. That should help you identify the problem pretty quickly without having to set up extended events.