That is what I meant. But objects as large as hammers have enough internal thermal interactions that spontaneous events are usually limited to individual particles within the hammer.
I am describing quantum events, of course, and although large objects can experience spontaneous events, it is usually confined to subatomic particles. So, for example, the radioactive decay of an atom is entirely and demonstrably spontaneous, with no specific triggering cause. Photons of light form continuously in empty space for no reason beyond random chance, and these photons can be measured from the pressure they exert on surfaces.
The big bang theory, as you must know, proposes a very specific expanding subatomic particle-sized seed for the universe. Since time as we know it started at that event, there was no time preceding the event to allow for a cause, since caused occur before effects, and there was no time before. A spontaneous, quantum event.