You can use
s = randi(n, e, 1);
t = randi(n, e, 1);
G = graph(s, t, [], n);
which will give you a graph with n nodes and e edges. Note that G may have multiple edges connecting the same two nodes, and may also have self-loops (edges connecting a node to itself). If you don't want repeating edges, use the following instead:
G = graph(true(n)); % Self-loops are possible
%G = graph(true(n), 'omitselfloops'); % Alternative without self-loops
p = randperm(numedges(G), e);
G = graph(G.Edges(p, :));
