Not to discount what rplatt56 said, but hesitation and shuddering unlike what it was when you 1st got this truck is NOT normal. Maybe common, but not normal. If I can throw out a guess as to what you are describing, I'll take a stab at it. Thru LOTS of research and trial and error and cash, I found what was causing my '02 F150 Super Crew FX4 to shutter all of a sudden intermittenly.
When it started I decided to dump some $ in it by changing out all the plugs, fuel filter and PCV valve. I also dumped in some STP fuel system cleaner. Started it up and it, the shuttering like hesitation, was still there sometimes. Hours of searching the web for the magic bullet fix turned out as a bunch of people guessing at the problem that apparently lots of folks are having. I followed some leads like the MAF sensor was dirty, so I cleaned it. No fix. Then I tried a lead about the throttle body ports being clogged and a dirty throttle body. I cleaned mine with some TB cleaner, NO fix for me, but I've heard that some folks with the 4.6L sometimes get an accumilation of carbon that restricts the air flow from the EGR. Most times it wouldn't throw a code as to the problem, but when and if it did it pointed toward a bad coil or misfire or EGR issue. I got a local mech involved but wanted to stay clear of the dealer for fear of getting robbed. Turns out I robbed myself in the long run. He said it was 3 of the coils because they were weak. Changed them out and it was still there. He then benched my fuel injectors. No fix. Then back to the mech a few days later and he said it was a vacuum leak. A few suspect hoses later and no fix. He kept it overnight and then put a new EGR on it. No fix. I was frustrated and he threw in the towell. I drove it straight to the local dealer. The next day I got a call to come pick it up. Turns out it was the DPFE sensor flaking out at times. They went right to it and my truck doesn't buck like a wild stalion any more.
Here's what I replaced before the problem was finally diagnosed by the dealer:
-3 coils and 2 boots -I'd bet the bank they are still good!
-1 EGR valve -Same bet.
-1 PCV valve
-8 plugs- they were due w/ 80,000 miles on the truck.
Also was the fuel injector cleanings, some vacuum line swaps, throttle body and MAF sensor cleaner, the STP fuel systen cleaner, LOTS of brain cells and all the hair I pulled out that will never come back! Plus all the labor involved by me at 1st and then the several hours I owed the local mech for his time ($$$). All because I was too stubborn to take it to the dealer in the 1st place. The dealer ended up charging me soething like $268.00. It was an hour labor, 1 diagnostic and the DPFE sensor to the EGR valve. VIOLA, it was fixed.
Here's a link about it that I found after the fact:
I hope someone gets some use out of my rant!