Shakes and anxiety are definitely common side effects of herb. We've read this very same complaint about 10,000 times here. Read any sort of general info on cannabis on Erowid or elsewhere, and you'll find shakes/panic/jitters listed as a common side effect. Happens more with people who're feeling nervous before they smoke and newbies. Happens a lot more with sativa and/or sativa-dominant strains, which can make even the calmest people jittery. Happens particularly within the first half hour after smoking, which is when you have the strongest "adrenergic" response (like you've had a burst of adrenalin) and the peak vasoconstrictive effects. Try switching strains, finding something with more Indica characteristics. If you're well exercised beforehand, that'll help you be more chilled out. Deep breathing and relaxation exercises can help you recover your balance, but some people have serious ongoing trouble with these side effects and some truly find that cannabis doesn't agree with them.