What's the noun for involuntariness? Here's the word you're looking for.
volunteer
One who enters into, or offers for, any service of his/her own free will, especially when done without pay.
(military) One who enters into military service voluntarily, but who, when in service, is subject to discipline and regulations like other soldiers; -- opposed to conscript; specifically, a voluntary member of the organized militia of a country as distinguished from the standing army.
(law) A person who acts out of his own will without a legal obligation, such as a donor.
(botany) A plant that grows spontaneously, without being cultivated on purpose; see volunteer plant in Wikipedia.
A native or resident of the American state of Tennessee.
(philosophy) A doctrine that assigns the most dominant position to the will rather than the intellect.
(politics) The political theory that a community is best organized by the voluntary cooperation of individuals, rather than by a government, which is regarded as being coercive by nature.
“Their traditional, voluntarist rides were losing out to the modern, glitzy sportive.”
“In the late medieval period, voluntarist theologians such as William of Ockham and Gabriel Biel radically distinguished God's absolute freedom and God's covenant relations.”
“A review of the Italian political thought of the 1920s also discloses deep associations between a rightist voluntarist model and a leftist organicist ideology of the social.”
“The distinction between freedom and voluntariness is explicit in the discussion of moral virtue by Spinoza, Gilson, and Murdoch.”
“Potential subjects would be told of these mechanisms to ensure the voluntariness of the consent during the free and informed consent process.”
“The stipulation was founded upon the fact that at the last trial they did take care of the matters as to the voluntariness and intelligentness of the waiver of those statements.”