Tick, Tick, Miss

I have an intermittant problem with a "lifter type" sound coming from my engine. When it does 'tap', it also feels & sounds like it's missing. Then, just as fast as it started... it goes away and runs fine. Then wiyh in a few minutes it starts over again. Is it possible that it could be a broken spring? It's jsut strange how it comes and goes. Sometimes, if I turn the engine off then immediately start it again, the noise goes away. Any ideas?

Seafoam? transfluid? MMO?.... I already tried all these. lol