It sounds like your laptop is posting, then looking for the hard drive... An issue with the hard drive (i.e. failing or corrupted boot sector) would cause this problem.
There may be an option in bios (f2 *I think* at Lenovo screen to enter bios) to not automatically restart on error, to stop the looping and possibly see a specific error.
Lenovo, like Dell, may have some hidden diagnostics options at startup as well that can SMART test the hard drive. However, you'll have to contact Lenovo for that.