I noticed the other day that every character I've created has had the same kind of hair and was a bit surprised. Does anyone else have any traits that are consistent across the different characters they've made? Is it intentional or just chance for you?

Every character I use is named a variant of 4 different names.  After over twenty years of doing this with PnP games and video games... I can't imagine me naming them anything else.

I play with someone who names characters after food as a theme. Different characters with the same name also ties into your avatar well :D 

I have noticed a trait among all my characters through the years.

They're all jerks.  

 ...I have no idea why.  ; )

my character backgrounds tend towards the emo/maudlin.

My characters have always ended up chaotic-neutral, no matter how I try to roleplay them. So, over the years, I just default to that one and save the hassle of a DM that cares wasting time keeping up with my actions, lol! 

Side note: I'll take 90% of the blame for the change, but sometimes... things just happen. The most recent slip towards darkness was when my Fighter tried to stop a guy that running away and I ended up rolling 20. Don't use kamas to try to stop someone on the move.

My characters always wind up neutral good.  I don't know why that is.

I've also noticed I prefer light or medium armor for my characters, unless their mages.  Even if I'm playing a front line fighter, I don't use heavy armor.

And when/if I choose multiple languages I always go for Elvish and/or Orcish.

I have played many clerics, all of them female humans, and all of them have had the same name. I just imagine she's been reincarnated dozens and dozens of times.

Then there is my "redneck" wizard. Imagine a skinny Hulk Hogan, long stringy blond hair receding above the forehead, and long blond handlebar mustache.

Each one has similar features to other characters I've played since 2nd. Backgrounds always change but some attitudes come through each character I play. Most of the time I play them as I would if I were them and if I start off as a Lawful Good I useually end up Lawful Neutral lol. Except for one Chaotic Evil guy I use in 4e campaigns some times. I always feel dirty and odd after I play him and most people are freaked out by him. Kinda fun but odd.

So far, most of my characters have been built to be capable on their own. With the exception of a squishy Wiz/Bard, they are all capable of hitting hard, and getting out of the fight. IMO, the best defense is not being in range I guess. I tend mostly towards light/unarmored characters, so Monk and Rogue work well for me.

I do have some players that have very consistent traits for their characters.  My Wife is a perfect example.  She will normally pick a Tiefling as her race and has a Paladin and Bard she loves to play.   I could say the same for a lot of my players that the race choice will be the one consistent trait.  That normally has their description very similar to each of the present and past characters they play.   Some people just like to play a dwarf and only a dwarf.  

Backgrounds are mostly the same as well, with a little variation depending on class.   Character personalities are often consistent with the player.

I do have one player who is a character actor and his characters are always varied with definitive personality differences and alignments.  It's always a delight to see what he brings to the table.  I want to find more players like this.

It's really difficult to develop a devise set of different personality traits without your normal self eventually showing. 

Yeah pretty typically chaotic good here lol

All my characters tend to be cocky, masters of "winging it", and are all horn dogs. 

I developed an accidental habit of all my characters at the time being related to each other...

Most of my characters tend to be aligned somewhat neutral.

All of my characters have the same last name, 'Hastings.'

I often use variants of the same names, and most of my characters have some form of stealthyness, even magic users lol

Every character I play has punx in the name and I treat it like they are all related even thou th races may very. The funny thing is the family patriarch had never been put to paper is basicly a legend (no details only rumors) and does not contain punx. All because I needed s back story for a sword.