It really happens naturally. It's very common to have placenta previa in early pregnancy. I had it still at 20 weeks but it lifted before 32. Normally women don't have limitations until it is closer to the end of pregnancy. What are your doctors saying?
You should do the yoga poses cat/cow. My prenatal teacher told us to do those as many times a day as you can. It creates space so the baby can move
If the placenta is what is covering the cervix, just time and the uterus continuing to grow will help it shift (if it is going to).