。
My daughter is slow to get moving, and it's a problem.
Literal
My [genitive-の] daughter [topic-は] butt [subject-が] heavy [reason-ので] troubled.
A body-part personality idiom. 尻が重い (literally 'heavy butt') describes someone who's slow to get up, procrastinating, reluctant to act — sluggish in initiative. The opposite 尻が軽い ('light butt') means 'quick to act,' though depending on context it can also carry the sense of 'flighty' or 'promiscuous.' A vivid metaphor typical of how Japanese pins character traits on body parts.