Easy to check. Just view your photos and rotate the phone.
If it takes 5 seconds to rotate, then you've got it. Restart the phone and all (rotation) is good until you use specific apps (like Lumia Camera 5) and it slows down auto rotate for entire phone again.
Remember to back up your phone data if hard resetting. I bit the bullet only after 2 days because it really slows the ability to take quick photos/videos.
Of course, if your phone rotates within a second, then you have something different, a hard reset may not fix it.