wondering if this has happened to anyone. everytime i start my car there is a violent rattle coming from my head and it almost sounds like my valves are starving for oil slapping up and down. now my oil is fine, i just changed it with 5w-30, i am not overfilled or underfilled. kind of stumped at the present time so any feed back would be great. keep in mind that it only happen at start=up and only lasts a few seconds.