After restart again today I got the same problem. Today I had to change back the account to built-in account to make it work. The built-in account is "Local system" which I just found in "sql configuration manager:"
So it seems this problem occurs every time computer reboots. Is there any permanent solution for this?
yes it happens again and again but not on every reboot but most of the times(even today it happened). But I know the solution just play with user account and get back to previous account, it would work. It would be better if I'm able to find exact problem and sort out permanently though.