Can taking prenatal vitamins give you energy?

Possibly: Depends on your diet - nothing replaces good nutrition, rest and fitness. Some vitamins - b's - and minerals like iron can support energy levels.

If you are deficient: Whether a vitamin gives you energy depends on whether you are deficient in it. If you already have enough then taking more won't increase energy. But most people have suboptimal levels of some vitamins & minerals, in which case taking a vitamin may give you more energy. Pregnancy can increase your need for certain vitamins.