Plasmashell start late

[MERLIN Philippe]

Hi!
The system is an Debian Sid AMD64 up to date, I am 
confronted with this problem which bothers me,  Why when 
opening a session Kde by sddm plasmashell is launched last 
so that on the screen all applications that were active at the 
closing of the previous session are already started without 
that neither the background  screen or the task bar. Which 
gives an unfinished aspect to Kde nor professional.
Philippe Merlin