Mass matrix error with degree of freedom and scale parameters of Student T distribution

Well, I would like to know two things:

  • What would be suitable to use as init in sample part for the posterior traces when I have the case where my scale, location and degree of freedom parameters around the range of range of (Ex: 0.00xxx, xx.x*10-x)?
  • What range of values I should use in the priors where my scale, location and degree of freedom parameters around the range of range of (Ex: 0.00xxx, xx.x*10-x)?