RepairPal Certified shops can diagnose and repair your 2006 Subaru Outback. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
I had this happen to me with my 2006 Outback 2.5i. It was a bad plug that was misfiring. If you have not already, you will want to have the plugs and wires checked.