when i used to get rrrreally high as a noob i would shake too, but just last week i got my hands on some really good sativa, and the same thing happened. i think it's just your body's reaction to such a quick dose of strong shit. if you're smoking more, perhaps you don't have a high tolerance, and you can just smoke smoke smoke until you choke choke choke. but don't choke.

the shaking usually goes away in about 5 or 10 minutes for me. i've never thought i was dying because of it, though, but i'm sure if you don't know what it is you'd be likely to think that.