Yeah, sounds normal to me.
My ds (now 4.5) has spent the past year regularly throwing tantrums over little stuff, generally clothes (he's a junior fashion victim) and food (availability or lack of particular items).
I've had the distinct impression that sometimes he just wants to fight, and will pick whatever issue he can find to throw a massive strop about. In these situations even if he was actually given whatever it was he was creating about, he would just move on to the next thing.
I think being four seems to be quite tough on little boys: on the one hand they have a powerful urge to rush around kicking, shouting, and smashing stuff, and on the other hand they're becoming much more thoughtful and aware, and realise how small and powerless they actually are. It seems to be hard for them to hold it all together sometimes.
Not letting him get too hungry helped, as did very early bedtimes (seriously, he was sleeping from 4.30 or 5pm till 6.30 or seven in the morning). Lunchtime sleeps too, if he wasn't at nursery. Trying to get them to talk about what's going on at school, and develop a language for discussing their feelings. Lots of hugs and cuddles and stories, too. Otherwise my tactic was trying to stay very calm and constantly repeating myself without shouting. I tend to say that I don't like being shouted at, and I'll only listen to people who talk to me properly.
I also found that acknowledging his anger seemed to calm him down, as did letting him know that we knew it didn't feel nice to be that angry. Admittedly you sound like a mad therapist crossed with Joyce Grenfell, saying "Poor you, you're very angry, aren't you. It must be horrid to feel like that." but shouting back just seemed to up the temperature even further.
hth -- he is still your lovely little boy, and it is just a phase you need to help him through!