How to combine multiple row vectors into a single row vector using loop?

A= [1 2 3 4  
    2 3 4 5  
    4 5 6 7  
    .  
    ....]  

where each of the rows is stored in a separate vector as such

a1 = [1 2 3 4]  
a2 = [2 3 4 5]  
.  
.  
.  
an = [1 2 3 4]  

and I need to create new cells, using a loop, containing all previous row vectors as follows:

vectors = {a1, a2, a3, ......,an} 

in the workspace I get vectors as a 1 x n cell and in each cell containing its own vector; e.g. the first cell contains vector a1, the second cell contains vector a2, etc. I don't want to copy the code every time I have a different number of vectors, so I'd like to automate this.

You'll want to not hand-copy each row into a separate variable before doing this. The proper way using your desired for loop would be thus

A = rand(15,39);
vectors = cell(1,size(A,1)); % initialise output

for ii = 1:size(A,1) % loop over all rows
    vectors{1,ii} = A(ii,:); % store each row in the cell
end

To do this without a loop (thanks to @beaker)

B = mat2cell(A, ones(1,size(A,1)), size(A,2)).';

though a matrix (so your original A) would be the best overall, since MATLAB works best with matrices.