Upvote:5
If you have a valid Schengen visa, you do not need a visa to travel to Mexico as an Indian citizen:
Holders of any valid U.S.A., Canada, United Kingdom and Schengen visas (any nationality) DO NOT require a Mexican visa to travel on business, tourism or transit purposes only. The length of stay shall not exceed 180 days.
Source: https://embamex.sre.gob.mx/india/index.php/visas
The fact that your Schengen visa is not used yet does not affect its validity.