Sometimes I do temporary work through staffing agencies. It's happened on a few occasions that they present me with "paper work to fill out" after the work has ended and before I receive pay.
Recently I replied to an ad where a marketing company needed a truck unloaded. I did the work. It was very simple. Now they are telling me I need to register with their online system to submit my invoice, and parting of registering includes signing a contract. This contract includes non-solicitation, confidentiality and indemnification clauses and some very broad terms. It's also very poorly written as it switches between calling me a "contractor" and "consultant". There may even be a term that conflicts about allowing the company to film me for commercial profit, because I am part of a film union (though this is likely a non issue for some technical reasons).
I've had some very unfortunate situations where I've been tricked into signing things that weren't fair. Now I'm paranoid when it comes to accepting contracts. I am not interested in working for this company again and would rather not take a risk by signing the contract. How can I politely let them know that? (I'm guessing some people are going to say never work without a contract, but in a sense the ad stating "move boxes for x hours for $y pay" was the contract. Also for such simple work it doesn't seem necessary).
PS I had posted on interpersonal.stackexchange.com but they told me to post it here.