"Your computer restarted because of a problem"
MBP early 2008 15 inch 10.11.6 is restarting when starting up.
MacBook
Boot into Safe Mode, and try again.
If you don't have a complete and current backup, get one right now. This as one of the common causes for this sort of problem can be failing hardware. Memory, disk, etc.
Run the hardware tests. Newer Macs will use different diagnostics than yours.
Some hardware failures can slip by the tests, unfortunately.
There was a graphics hardware recall for some MacBook Pro systems from that era, though that program expired in 2012.
If Safe Mode works and if the tests don't show any hardware errors, and if you have any of the following installed, remove any add-on anti-virus and anti-malware, and remove any add-on cleaning tools or performance tools, and remove any add-on network-firewall-and-monitoring tools. This removal of each per the vendors' instructions, rebooting, and trying again.
