Long time to load 18.04.2

I just installed Debian and I have Ubuntu 18.04.2 on another partition. It took about 40 seconds for Ubuntu to load, but it now takes almost 3 minutes.
My dim (80 years of memory) tells me that the uuid of the swap partition can be modified by a new installation and that existing installations can take a long time to solve this problem at startup. If it's the cause, can I fix it? If this is not the cause, what can I do?