When you call Frankenstein ponderous, it's not because he likes to ponder the great questions of life. It's because he moves like a Mack truck, only slower and less gracefully.
Ponderous also describes a person's manner, or their manner of speaking. If it does, this is a person you will want to avoid. They're solemn, speak slowly about things that are boring, and get to the punchline of a joke about seven years after anyone with half a brain has figured it out for themselves.