BMW Repair: WHY WOULD, 2000 bmw 540i, bmw 540i

Question
WHY WOULD A STARTER HAVE POWER THEN LOSE IT WHEN TRYING TO  START THE CAR ON A 2000 BMW 540I? THE BATTERY IS GOOD I CHANGED IT .CANT FIND ANY LOOSE WIRES ON THE STATER  AND LIGHTS DONT DIM SO ALT LOOKS GOOD.

Answer
Leo,
 Sometimes starters get whats called "heat soak".  This usually happens after you have driven the car and the engine has warmed up.  Since the starter is mounted to the side of the engine it absorbs heat and will sometimes cause the starter to get stuck, preventing it from turning.

 This has happened to me, and I've taken a hammer and gently tapped on the side of the starter while someone is turning the key.  It has broken it loose for me.  This can happen to new or old starters.
 
 Good luck,
 Josh