If that is your problem, have I found the solution for you. It keeps you hands steady, your fingers out of the way of the lens and it lets you hold your iPhone (or other smart phone) comfortably while you shoot. And it fits into your pocket or purse (at least my pocket is big enough). It is the “Slingshot” from a Kickstarter funded company named Woxom.
Your smart phone (any size even with a case) fits between flexible holding prongs and you are set to go. It can be used horizontally or vertically and the pivoting handle can adjust to almost any angle.
It has a small built in tripod that is stored within the handle. And the great part is that the handle can be unscrewed and the frame has a screw fitting that allows it to be attached to your own tripod. I use my iPhone for longer video interviews and keep it on a regular small tripod to keep it eye level with the person I am interviewing. For most other video shooting I keep it on its own handle which provides a steadier shot than trying to shoot with the iPhone alone.
Let me tell you it has been a lifesaver for me. This handy little device costs $20 and can be bought from Woxom or can be bought from Amazon.