Welcome to Healthcare Magic forum.
Yes it is normal and common to get penile erections at this age due to the physical and hormonal
changes occuring in body due to puberty
An erection is a hardening of the penis that occurs when sponge-like tissue inside the penis fills up with blood. Usually, an erection causes the penis to enlarge and stand away from the body.It is not related to physical growth of penis.
Although many erections are caused by sexual arousal, such as watching a sexy television show or fantasizing, many erections seem to happen for no particular reason.
Because erections usually aren't controllable, there's not much you can do to avoid getting them. Unless the penis is stimulated enough to ejaculate, time is the only thing that will help them go away.
As your hormones settle down and you advance through puberty, the frequency of unexpected erections and wet dreams should decrease.
Wishing you good health.