There is a very good blog by Jimmy may with some SQL Queries that gives you Wait Type, Finds out if there are IO issues, Blocking etc. Check this blog.

In that page there is a link called "DMV All-Stars Dream Team"

You can run the SQL Query based on your SQL Server Version. What I would look for if I were you would be REAL TIME BLOCKING and the Virtual File latency. The latter one will show if there are any problems with your IO subsystem.