Same issue.
Recently (Windows 10 Pro user, updates are current) every time I reboot computer, IE opens to the Goggle search page.. I generally never use IE (Firefox user) and only use IE for work log in page when working remotely. It is always shut down before I turn the system off. Firefox is last/current browser at shutdown.
I have checked Startup for IE (not there) , changed the IE page settings (as suggested) in IE and because IE is used by one of my VPNs for logging in - I can't just disable/remove IE from my system. I have run full virus scans and eliminated "redirectors/browser hijackers etc.
Because the regular Google search page always opens , even after I change the home page in IE to anything else...and save it.... I suspect this is more of Google somehow marketing itself on my laptop.... but until a few weeks ago.... this never happened.
As my Avatar indicates , I am not the guy to start editing my registry .... but at this point....