Nissan Repair: Starting, planetary gears, nissan maxima

Question
Hi, I have a nissan maxima 98.  the car is not starting properly. some day it starts normal. other days it takes a while to start or it start and cuts off. when starting the vehicle i notice a noise.  i changed the alternator recently (1 month ago)so i don't know what could be if it is the battery, starter or cold start.  appreciate you advice.  

Answer
I am wondering what kind of noise you are experiencing?  These are known to strip the teeth off the flywheel and the starter is prone to getting dry.  So, if you are hearing a really bad grinding it is the flywheel and that would have to be replaced.  If the noise is a deep whirring sound it would be the starter needs to be removed, dissassembled, and cleaned and greased.  The starter is an underdrive unit and the planetary gears need the grease.