Do you lube your slide (internals) and trigger assy? This can happen if you do.
Also, did you store your pistol, hammer down (trigger pull, without slide cycle)? Normally this doesn't have a negative affect, although your pistol can fly apart if dropped just right. How else could the striker have been extended? The safety button didn't engage, and the striker didn't engage the trigger, allowing the striker's inertia to strike the primer, or the striker was seized with the pin extended. Once the trigger is pulled, the cross-pin safety doesn't reset until the slide is cycled, at least far enough to reset the trigger (which is a LOT less than required to chamber a round).
In any case, it shouldn't have happened, unless something was wrong when you last fired it, before storage. A slide cycle should have reset the safety, and staged the striker to ready (pre trigger pull) upon slide release (should have remained in this position). So, at least 2 things weren't right: Cross-pin safety didn't engage; striker didn't engage trigger.
Excessive lube (lube where it shouldn't be). Broken/damaged/worn out part(s). One, or both. A perfect storm, regardless.
Life is tough. It's tougher if you're stupid. -- The Duke