Hi Bruno Souza
It is my understanding that you want to use loop variable j to create different symbolic variable names. Following code snippent might help to serve the purpose.
for j = 1:5 % line 1
symbolicvariable=strcat("x",int2str(j)); % line2
syms symbolicvariable real % line 3
end % line 4
line 2 gives variable names such as x1, x2.... xT which can be used as symbolic variable in every iteration.