2004 Wideglide, most of the time when starting when I push the starter button it sounds like the battery is dying, then it cranks. The battery is good. Could it be the starter relay or the starter itself. Is there any way to check them with replacement or disassembly?

 

How old is your battery?

 

Unless you had the battery load tested, you don't know if it is really good. Now if you've done that, check the cables to the battery and ground and make sure they are tight and clean.
It wouldn't hurt to pull all the fuses and relays to check for corrosion on the contacts. It doesn't sound like it could be the starter relay, but those you can get at an auto parts store for a couple of bucks.

 

What Nevil said