In this paper, we propose a Markov Chain Monte Carlo (MCMC) algorithm to handle fog nodes coalition formation problem. The need to construct coalitions emanates from the fact that some nodes could not be able to handle the required computation on its own due to their limited computational capabilities. Also, we introduce a set of constraints on the formed coalitions. Specifically, nodes could have preferences with whom to coalesce. Even more the formed coalitions have to be of semi-equal computational powers.