Hello Preetham
from your logs and inputs I would say that SonarQube is receiving GET requests on its SAML endpoint URL, requests it is not able to handle (as it only expects SAML responses from your IdP using POST)
Did you set your IdP login endpoint as SAML login URL parameter SonarQube side?
You may check for received requests in access.log file.
Best regards
Sylvain