Does sealant in tubeless tyres slosh around? I'm getting interested in tubeless tyres for my gravel bike

I'm curious about the liquid sealant that you put in the tyre. 

As I understand, it should stay liquid so that if there is a puncture, the sealant will flow to close the hole.

Does it slosh around in the tyre as you ride it ? do you feel it moving ?
Tubeless sealant has the consistency of roughly soy milk. If you take a tubeless wheel and shake it, you should hear the sealant sloshing around (and if you don't, chances are it's time to add sealant). You need to have liquid sealant to help seal punctures; if its solid and dried out, it won't be mobile. 

Will you hear it when riding? No. There are far louder noises in normal riding, particularly wind and tire noise anyway that would prevent you from feeling it.

Will you feel it? No. There's not much sealant in a tire -- on the order of tens of grams; it doesn't have the mass or speed of movement or consistency for you to notice that it does move (it's not like you're putting a bunch of ball bearings in the tire -- its a sticky yet relatively free flowing liquid).