Can I use Urn of Vitality to shuffle the card Impact Energy from my discard pile into my deck?
No, you cannot. Urn of Vitality is only able to target a specific card named "Single Strike Energy". Although Impact Energy is a "Single Strike" Energy card, it is not "Single Strike Energy".
Source: Chilling Reign FAQ; TPCi Rules Team (2021-06-17)

Relevant cards

Note: All applicable cards may not be listed below.
SWSH5_139
SWSH5_139
SWSH6_157
SWSH6_157