You don't need Berserk to freeze time, only Assassin Rush and also a spade, fishing pole, or unopened chest.
Assassin Rush through any gate that you can run back through without bumping into anything. As soon as the load screen comes up, hold back on the left thumbstick so that you automatically run back through the gate. If you bump into the gate on the way back through, it will not work. Take out your bow and fire an arrow to see if it worked. Don't zoom in with the bow, just fire an arrow.
Dig, fish, or open a chest to unfreeze time.