There is an argument against free-will that goes like this: all actions are caused, and if it's caused it's determined and not a free choice. But, even if an action was not caused, it still wouldn't be a free choice, because if an action isn't caused by anything then it's random.
But there is a difference between a cause and a motive that is relevant for discussion of free-will.
People can be *caused* to experience something out of their control. For instance, if Ted is pushed out of a window, he is caused to hit the ground and be injured. Here we can say that it was determined that Ted got injured (it was determined by the fall).
But if one is 'motivated', instead, then the implication is that one is only encouraged towards an action, but might not take it up. With motivation, the future is open. For instance, if Bill is thirsty, he is motivated to go get a drink, or ask someone to bring him a drink. But his motivation alone does not guarantee that he'll do either of those things, he might pick staying thirsty.
So it's simply not the case that a free-will advocate is limited to only the options that actions are caused or random, there is a third category.
The determinist can only argue that the third category doesn't really exist--that motivation as so defined is a myth. For instance, they can say that Bill thinks he chooses to stay put rather than go get a drink to sate his thirst, but really circumstances mean that Bill would always make that 'choice' and not another.