Rookie - 6.7 bad battery or relay/starter?
 

Got my first diesel 4 days ago used. 62k miles 2014. Took it to TWO different mechanics not related to dealer and had them check it out both agreed it was in basically flawless condition. Carfax was also perfect. Then this happens........
It ONLY occurs on the first startup after being dormant for a few hours (usually longer than 3) and the severity of it depends on how long its dormant. Although in truth the video i took above was probably the worst. Say i crank it and go drive for 20 minutes then get out for an hour and come back itll crank immediately. I live in lower alabama where its 49 degrees outside so its not the cold.
Anyone got any ideas on what it is? Id like to know what I'm about to get myself into before i take it to the shop.

Ok its a 5 pin relay under the hood,, swap them around, Ild have to go look at mine, but its one of the big ones..Mine did the same thing..