Responses
Maybe one of these...
https://www.mangago.zone/read-manga/tensei_goblin_dakedo_shitsumon_aru/
https://www.mangago.zone/read-manga/i_reincarnated_as_an_sss_ranked_goblin/ though he's a kid, not really a baby
https://www.mangago.zone/read-manga/tensei_shitara_slime_datta_ken/ has a goblin-like form even though he's not a goblin (I think)
ML reincarnated as baby goblin.