I have a smartphone now at least, but its still equivalent to one from 2011 or so.
I dunno entirely as to the shaking, i used to have rock steady hands, so much so that I was going to be a neurosurgeon (that went away for other reasons, not the shaking) but i've just lost my steadiness, and its worse after i injured my hand pretty badly 6 months back.
As an armchair doc, I've determined that I have Essential Tremors after hearing Sal on the Howard Stern show has it. Interestingly enough, I also badly injured my hand (although it was the left and I have shaking in both hands). I generally make it worse by constantly thinking about it in some public situation where I might have issues.