This still happens to me, but my teacher gave me a tip to stop the shaking while drawing.
1) Place two dots randomly on a paper
You can’t force yourself to draw. You have to make sure your comfortable, in a cozy chair. Don’t put all the weight on your wrist, keep your weight on your elbow. When you put your weight on your wrist, it’s not going to move smoothly.
When it comes to drawing, quality is number one when choosing a product. As you saw from a few of my photographs I use prismacolor markers and colored pencils. The following is what I have along with the approx ( I don’t remember) price I paid.
Graphite Pencil Hb, 2B & 4B ( About $2.00 Each)
Mechanical Pencils (like $2.99 for a simple pack)
.005 Pen (I got the set with 4, comes out to $18.99)