Starting and Running Problems 01 Boxster S
 

Help me PLEASE!
On 08/16 I parked my 61,000 mile Boxster S for 6 days. Had to key open the door (sleep mode??) Car started and run rough for about 10miles. Was fine until 08/25. Parked it in the evening 5:00, after work. Went to move it about 10min's later, starter clicked, windows went up and down...wouldn't start. Charged the battery, left it over night. Started it the next day(Wed.), ran it and drove it yesterday to work. On the way home from work it didn't seem to run great. Parked it, then tried to start it. Wouldn't start. So I 2amp. charged it all night. This morning it started and I took a meter reading before going to work.The readin was 13.88volts.Droove to work (12miles) and the reading before shutting it down was 12.3volts.
P.S. belt is intact and I had the battery checked on Tues at the Auto Zone. When they first checked it before a half hour charge, it read 12.4volts...under load it dropped to 5.7volts. After the charge it dropped to 11.4volts under load, but went back up to 12.4 volts.........Read Good Battery.
What can be wrong??? I've heard 99's,2000's, 2001's may have problems. Can anyone help??
Thanks, Denny