454suburban

Hello, This is my first post on a Forum in general so I hope I do this right.
I have a 1999 Chevrolet Suburban with the 454 and Im having some starting problems with it. First thing in the morning, ill get in it, turn the key, and itll fire up instantly. You will barely even hear the starter turn the vehical over. But when i drive it for a bit, get it to operating temperature, and go into the store for an example, Ill be in there from 30 minutes to an hour tops, and when i get in it, start it, It will crank for about 10 and sometimes 20 seconds. After about 6 or 7 seconds, i stop cranking it, give the starter a break, and try it again, for another 6 to 7 seconds. Usually the second set of trying to start it, it slowly fires up. Not instantly tho, It sounds like maybe 1 or 2 pistons are fireing then itll build revs and itll idle perfectly like nothing was ever wrong with it. It drives perfectly, you can floor it from a stop, and it will just go. When It struggles to start, i do notice some white smoke but only once it tries to start.
I replaced the Fuel filter, Battery, and checked the fuel pressure and it all seemed to be fine. I do live in a very cold environment but in the summer it gets to maybe 90 tops, and it does this every time reguardless of the temperature. I am not a fan in taking my vehicals into the shop because I made the mistake once of letting someone do my oil in my truck I used to have, and they didnt put oil in the thing... But thats another topic.
So if anyone has any advice or has ever had these problems and managed to fix it, please let me know. Suburban only has 120k miles on it, and it for being 16 years old, I am really happy with that.

here are some youtube videos of it happening: