plasmashell and activity of CPU

[phil-deb1 . merlin]

Hello,
On my computer my system is Debian Sid AMD64 up to date, 
suddenly the activity cpu increase until reach the maximum 
100 %, the top command indicates the culprit " plasmashell " 
if we kill it and restart plasmashell the activity of cpu becames 
normal 5%. 
The problem is new, at the very beginning of kde 5 it existed 
but since it had disappeared.
Met you the same problem?
Philippe Merlin