Is it normal to have erection without thinking in anything sexual?!

It happens. You are right in the middle of puberty & your male hormones are raging from one end of the spectrum to the other, trying to figure out where to settle down. This causes that little feller to have a mind all it's own & there's nothing you can do but learn to live with it - just like evey other male on this planet has had to do.

Yes, what you are experiencing is completely normal. You can have a dream that's not necessarily erotic, & you will have an erection.
At your age, your hormones are doing great things..& you can't control them. I'm sure you've noticed an erection when you get the urge to urinate. That too is completely normal. You can wake up with an erection & not remember dreaming anything in particular..that is also normal.
All of this is part of your maturing process. In time, everything will settle.

Yes. You are approaching your sexual prime (18).

Some reports indicate that men think about sex every 7 seconds. You may not even realize that you are thinking about sex.

Often times men will get an erection as their bladder is full and the pressure is pushing on your "wood" muscles. Most often in the morning.

Yes! I get erections every day it's nothing to worry about. Although you don't like them very much it's actually quite normal as you are going through puberty. Noting to worry about. Honestly!

Experience

yes! that is totally normal! It is a natural part of puberty...when i was going through puberty ( i am thirteen but done with puberty) it will do that for about a year...

Yes, your hormones are going crazy right now and it will happen. They will level out soon, nothing to worry about.

Yes. When your bladder is full of urine, early in the morning and also during the night.

its probably because you dont touch yourself at night enough.

your window

Dude the best part of being 15 was getting hard especially when the wind blew.

Yes.