M156 hard start crank issue 2008 s63

This issue was there before I did the entire engine rebuild. New starter, new starter battery, new Crankshaft position sensor, tons and tons of new sensors/parts. New injectors, fuel pressure is normal. No check engine light when engine eventually starts. Starter is grounded. Fuse 21 is good.
The key is aftermarket. The camshaft position sensors are old (no camshaft codes however).
I’m at a dead end. Not sure what to do. It occurs more frequently during cold starts. Once heated up, doesn’t take this long. Engine runs super smooth with NO CEL once it’s started.
Fuel pump works as it should. Fuel pressure sensor? But no code for that.
Any suggestions?