Whether your new boss is rubbing your shoulders as a (clumsy) form of flirtation or as a power play, it's inappropriate. There's a rule that applies whether you are 5 years old or 105 years old: If someone is touching you in a way that makes you uncomfortable, you have the right to ask them to stop. Your body is your own.
This is your brand new boss, so understandably you are unsure how to proceed. Here's my advice on the steps you should take.
1. Tell your boss in plain English that you are not comfortable with them touching you. Be firm, polite and direct. Say "I do not want you to touch me. I am not happy for any colleague to do that and I want you to stop."
2. If you get an aggressive or otherwise unfavourable response from your boss, and the shoulder touching continues, go to your human resources department or your boss's line manager.
3. Direct your boss to this definition of sexual harrassment if you're in the US. If you're in the UK, show them the way to this.
