MacBook Pro 17inch early 2011

So are you saying you are unable to boot into Safe Mode or Internet Recovery Mode (Command + Option + R) because the system reboots before it reaches the login screen or the online recovery tools?

Or do you get some sort of error message when attempting to boot into Internet Recovery Mode?

Try booting the online Apple Diagnostics to see if any hardware issues are detected.

More than likely your laptop has a hardware issue. The two most likely things are a failing hard drive or a GPU failure since the 17" model is known to have GPU issues. A failing internal hard drive can prevent a computer from booting even to external media.

Hello Sidthemowgli,

If you're Mac is restarting unexpectedly, we recommend trying to resolve the issue by following the steps here: If your Mac restarted because of a problem - Apple Support

If the issue continues after following those steps, Get Support from Apple Support

Thanks.