It is the tires. From sitting they get a 'flat spot' which in cold weather takes awhile to go away.
I suggest adding a few extra pounds of air in each tire in cold weather to reduce the problem.
Also, some tires are much worse with this issue than others...
In cold weather nearly all tires have this to at least a minor degree.
Your new shocks may be making it way more noticable.. being a little stiffer too.
One minor way to lessen it is to drive in a tight circle a few times. The flat spots then stop being in the same place as the tires move a different distance in the circles. So the bumps are 'spread out' instead of all four at once.