to begin with vs in the beginning

to begin with and in the beginning both are adverbs.

Word	Noun	Adjective	Verb	Adverb
to begin with	No	No	No	Yes
in the beginning	No	No	No	Yes

As adverbs, to begin with and in the beginning are synonyms defined as:

Other synonyms of to begin with include earlier, in the first place, originally.

to begin with (adverb)	in the beginning (adverb)
before now	with reference to the origin or beginning
	before now