CLK320 Sluggish Start

My car has recently been slow to start. I
can hear the starter cranking for several
seconds before the engine turns over.
Once it starts, the car runs just fine. Today
was the worst one-the starter cranked for
awhile then the car was completely silent
for a few seconds, almost as if the starter
gave out and the car died, then all the
sudden the engine caught and it started
up. There has been a lot of maintenance
and repairs done in the past 9 months
(after I hit 100k miles) including a new fuel
filter, air filters, battery, fuel pump, fuel
sending unit, cam sensor, spark
plugs/spark plug wires. Do you know what
the problem could be?