If there is no self, why do anything?

My limited understanding of Buddhism has already helped me in many ways and I am very glad to have found it. With that said, I have always wondered about this title question. If there is no 'I', then why do 'I' do anything? If we can consider ourselves to be just part of everything else, where does the motivation to do anything come from? Surely we admit that there is a self whenever we perform an action (and thus reveal a motivation that must have originated from a self). If there truly is no self, surely we would all just freeze motionless, die and return to nothingness. Apologies if this is an ignorant question. I am still feeling my way around this whole concept.