Much depends upon how heavy the coats you applied were. My 4 coats might be way thicker than your 4 coats.
Heavier coats will have more chance of urethane wave than lighter coats.
This is a hood that I sprayed some heavy coats of Euro clear on. This is as sprayed so you can see the slightly wavy look it has.
View attachment 11542
When you start sanding you will see where the surface is not flat. The low spots will remain shiny. The idea is to get the whole surface flat and level with your hard block. After that you can switch to softer rubber blocks while removing the previous grit sanding scratches.
Here is a picture of my signature car (first attempt at show car paint job - learned a lot sense then) after a little bit of sanding with the block.
View attachment 11545
In this next picture (different vehicle) the entire panel was leveled with 1000 grit using the hard block. A foot or so of the right side has been sanded with 1500 grit to remove the 1000 grit scratches. The difference is easy to see if you wipe with solvent based wax and grease remover and view the surface before it dries.
View attachment 11543
The next picture shows the entire panel sanded with 1500 and the bottom portion sanded with 2000 grit. The key is to be sure and remove all the previous grit sanding scratches.
View attachment 11544
Hope this helps.