Switched from sertraline 50mg to 100mg as per my doctor since i was still feeling depressed on 50mg is it safe to double the dose any side effects?

An increase by 50: mg isn't unusual. I usually ^ by 25 or 50 mg at a time.

Each case is unique: The most likely thing w/ respect to side effects is that you might again experience your original reactions. I.e., it's more about how YOU react than anything else. That is still a moderate approved dose so if you respond well for the aim, you'll be okay. If not - that's another question. Try adding CBT therapy to optimize results. Do not increase beyond 200 mg in search of success. Best!