Answer:
Your body is starting to mature. What you are describing is called an erection. It is completely normal. It is telling you that your body is ready to have sexual intercourse.
Also, your hormones are causing an excess of blood pressure. Blood pressure controls your erections, so you may get one at any time of the day. Do not think that it is telling you that you are attracted to your friends, because it is not.
~At age 13 it is normal. You are underage to be on ByeDr.com! We answered your question, now go ride your bicycle.~
It is normal. It is part of Puberty. You are fine. And, Yes it will stop.
not it will not but now when you are going throw teen you will have a lot. than you will have when you are a adult.