since your capable of booting it in safe mode, that would mean no hard drive errors, so take a moment and maybe a breather because thats instant relief for you. sounds like you most likely have a virus or malware/rootkit thats destroying the startup process, could be a bad program, bad file, something downloaded, etc. if a virus scan and malware scan and/or system restore does not solve the process, the only option is to back your important files up into an external drive and reinstall windows with a clean install.
if you'd like reccomendations for antivirus software or antimalware software,
Avast antivirus, and Malwarebytes antimalware are two great programs.