It depends on age of PC, if it came with Windows 10 pre installed it will be fed this update faster than a PC that was upgraded to 10.
If you don't want to wait - I know I didn't - GO to the
Microsoft ISO site
and either click 1st link to download the update assistant that will download 1903 and install it on PC, this will check PC before updating so if there is a valid reason you can't update, it should tell you.
or 2nd link to download the media creation tool which can also be used to update current PC or make a USB/DVD installer.
I would suggest making the installer as if you are having issues, it is a better idea to make the USB as then you only download the files once, not multiple times which could occur if the update process doesn't work