You are not alone! My DT girl had her first tantrum at 11 months. I didn't think kids could get them that young, and at first I thought something was seriously wrong with her! Scared me stupid, and then I realised it was just pure temper. She went through a phase that lasted for about 6 weeks where she would have about 4 days a week where she would have tantrums and in that day she could have as many as 5 or 6 episodes. She is now 22 months and now has them very rarely, though still more than her twin brother, who has never actually had one yet!!!
I found that it is nearly always due to frustration. Very understandable if you've got a bright child with lots of get up and go but who lacks the mental development to understand what it is they want, let alone the ability to express it before the frustration bubbles over into rage. You know your DS better than anyone, so my first advice would be to watch him closely and try to identify cues that he is about to have a tantrum. It's actually a lot easier than you think. If you can spot the signs before it happens, you can head it off through distraction. If you can't, though, don't worry. Don't forget that frustration is a big part in how children learn and develop problem-solving skills.
With my DD, if I can't prevent the tantrum I can sometimes calm her down very quickly by just picking her up and cuddling her. I don't say anything, just cuddle quite firmly. If that doesn't work and she's really going for it, I just make sure she's safe and ignore her tantrum but not her. I don't tend to tell her off as I feel that this could send two wrong messages - one, that it's not ok to get frustrated (which is stupid, because frustration happens to all of us, it's just a case of how you express it, and at 1 or 2, a child is incapable of expressing it any other way), two, I don't want to accidentally reward bad behaviour by giving a tantrum too much attention, and a telling off is attention, albeit negative. I just completely ignore the tantrum and treat her as if she was behaving perfectly ok. For example, if we were playing a game and she had a tantrum, I would carry on playing with her brother and occasionally look at her and invite her to play. I don't cajole or make too much effort though as this can be giving too much attention. I found this 'pretending it isn't happening' approach to be far more effective than ignoring her completely, which I find escalates things even more. By behaving completely normally, I think what has happened is that she has learned that tantrums don't have an effect - any effect. Ignoring her is an effect, even if it's an undesirable one. That said, one the one or two occasions where she has gone off on one to such an extent that I have been scared she will hurt her brother, the dog or herself (or me for that matter, lol), I have resorted to putting her in the playpen til she calmed down. The play pen has not been needed for 6 months now and has been put away.
Hope this doesn't sound too preachy. Just telling you what worked for me. Also ahng on to the fact that this is a phase, and it will pass. Best of luck.