Engine death rattle when starting

I've seen exact same thing twice in the last couple months, both times I noticed that the shown battery level was at 1-2 bars at start. I already know I have a weak hybrid battery, so I'm thinking its related. Lately the charge had been 4+ bars always, but I'll have to try depleting the battery and let it sit abit to see if I can recreate it.

 

might be hard to diagnose at this stage of the game, have you cleaned the egr circuit?
keep an eye on oil and coolant. if it gets worse, consider a head gasket test.

 

You don't come here much?

First thing in the morning, after a good drive the day before:

1. Remove wipers, wiper motor/linkage and cowl. (see video #13 here)
2. Remove ignition coils and spark plugs (When reinstalling, spark plug torque spec on reinstall is 13 ft/lb with clean/dry threads, you'll need a 14 mm or 9/16" spark plug socket)
3. If possible, remove engine coolant reservoir cap, and install gizmo to pressurize cooling system (to accelerate possible coolant leakage)
4. Run borescope down each spark plug hole, looking for evidence of coolant seeping past head gasket into cylinder(s). It's best to have a borescope capable of looking "over it's shoulder". You're looking for exceptionally clean looking piston tops (evidence of coolant steaming off crud), and tears of coolant forming and running down from the head gasket seam.

Has the EGR system ever been cleaned?

Info on head gasket and EGR in my signature. (on a phone turn it landscape to see signatures)

 

Very common early head gasket leak. Diagnose quickly and repair to avoid an engine replacement.

Car Care Nut HG Borescope at 660s

Block egr flow test to rule out sticking open egr. Even if egr if sticking it won't cause severe rattling that quickly clears for the rest of the day.

At about 10:15 in the video he starts talking about the egr valve letting "air" into the intake manifold. He means exhaust gasses.