Usually this is a sign that the battery has so little charge that it can't power a bootup; either the battery won't be charged or the charging system isn't working.The reason you should charge from the wall is it gives higher power output than the mac. This is all assuming that you haven't recently opened the phone to repair something, and, that you haven't dropped the phone or got it wet.....

Start with the easiest things first....

Look at the USB dock, check it for dirt/damage that may be stopping it from charging properly. Check your USB cord for the same thing.

Plug phone in to wall charger and leave for several hours/overnight to see if it charges, also to see if phone will hold the charge.

Have you dropped the phone? this would make damage to dock more likely.Open iphone using any guide on the right under the photo.. check that connector 4 is on properly

If you can't find anything glaringly obvious then you can either swap the battery, the dock or both.