I am thinking somehow one or more of the keys on the keyboard are stuck and it give a command to close the internet browser?!
such as Alt F4 or Alt space-bar and C?? (but Only the browser? dont make sense?)
have you unplug your keyboard and re plug it? turn it upside down and hit the keys/shaking it? you'd be surprise what falls out of there !
Oh I bet you have a virus. reboot in safe mode with networking go to one of those online free virus cleaning site (like pandasecurity, etc,) and let it do its thing for couple of hours.
I bet if u look in msconfig/startup there are bunch of unknown .exe files...(but not necessarily)