Can u die from myocarditis without knowing anything wrong ?

Yes: unfortunately the first symptom of myocarditis can be death. Myocarditis is inflammation of the muscles of the heart. It can be caused by infections, medications, some inflammatory disease, and illegal drugs such as cocaine.

Unfortunately, yes: Acute myocarditis usually results from viral infection of the heart muscle, and causes weakness and difficulty breathing. It often follows other flu-like symptoms by several weeks. An infrequent complication is sudden death due to heart rhythm disturbances. In most victims, the arrhythmias occur after the diagnosis is known, but occasionally death may occur as an early complication.