Yes, all Intel X86 CPU's start up in 'real mode' which is 16-bit mode.
They start this way because at initial reset none of the required data structures for protected mode operation (page tables, GDT, IDT, etc.) are present. So the CPU starts up as a very fast 8086 who's purpose is to setup just enough page tables, a GDT, an IDT, etc. to be able to switch into protected mode and continue system bootstrap.
They start this way because at initial reset none of the required data structures for protected mode operation (page tables, GDT, IDT, etc.) are present. So the CPU starts up as a very fast 8086 who's purpose is to setup just enough page tables, a GDT, an IDT, etc. to be able to switch into protected mode and continue system bootstrap.