Before I have sex I have to use my hand and masturbate for a minute or 2 before I get an erection. I don't ejaculate because then I'd lose it, I just have to make sure I get hard and then put it in. Is that bad? I can imagine some guys can get an erection just like that on the spot without doing anything with their thing. That takes away the awkwardness when it comes to having sex. Do some guys like me just need to "warm up" with themselves and/or the girl before having sex?

Same with guys. Some take off their trouser and out pops a woody, others you have to give their little friend some attention first to "wake the dragon"...
really, all people are a bit different, and thats totally normal. ^_^
only worry about your constitution if you also fail to HOLD an erection. some light endurance sports help supposedly.
A flying male genitalia with the basic mindset of a happy puppy and the life purpose of a vibrator.
Good boy!