Some people have an upset stomach that is very sensitive to vitamin C in its acidic form (ascorbic acid). I do not know exactly what sodium ascorbate is but it is probably ascorbic acid.
I have very bad gas problems with acidic vitamin C.
It does not matter when you take it, if your stomach is sensitive you'll have bad gas for many days after stopping.
That's why you have non-acidic vitamin C - called ester-C.
I use it and get no gas, as long as I stay within my body's requirements (which seem to be around 3.5g/day).