Colossus of Sardia

Oracle Text

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)

Colossus of Sardia doesn't untap during your untap step.

9: Untap Colossus of Sardia. Activate this ability only during your upkeep.

Card Rulings

5/1/2008 The ability that untaps it during your upkeep has been returned to an activated ability. There is no restriction on how many times it can be untapped during your upkeep with this ability.