OP, I was prescribed anti-depressants (not Setraline but Citalopram) in August of 2018.
I got the prescription and they sat in my drawer for a year along with a 10-day supply of Diazepam and a 28-day supply of Propanol.
The only thing I took were the Propranolol and they were useless. Designed to slow down your heart rate and reduce the feelings of anxiety. Maybe I was on too low a dosage but they did fuck all for me.
So for the next year I soldiered on. I went to CBT therapy, I meditated, relaxation techniques, you name it, I tried it. But that year was a living hell. I literally felt like I was going to drop dead at any minute. My heart was pounding ten to the dozen, and I could feel myself vibrating, literally if I sat still. My anxiety was off the scale and all I could think about was impending disaster and oblivion. When I put my head to the pillow at night the combination of the vibrating and the rapid thumping of my heart made sleep impossible. Looking back I don't even know how I survived.
In September 2019, I woke up in the night after being 'asleep' for less than an hour, alone in the house with my heart literally flipping inside my chest like a dying fish. I tried everything - breathing, meditation, took a double dose of Propranolol and nothing worked. I honestly thought I was having a heart attack.
I drove myself to A&E and was given an ECG and a different beta blocker - Bisoprolol - by the doctor at the hospital. It was like a magic bullet. What the Propranolol hadn't touched, the Bisoprolol nailed. I remember sitting at home the next day and not being able to feel myself below the neck. What I mean by that is, for over a year, whenever I sat still I could feel my self vibrating; my heart racing and thumping.The only way I can describe it is I could hear and feel myself living, like a machine running.
Now it was all quiet. it almost felt like I was dead but in a good way. That one little tablet, prescribed by the doctor in A&E had put an end to my physical symptoms.
What that taught me was - get the right drug! What works for one, won't work for another. Two beta blockers - one prescribed by a GP - useless, another prescribed by an A&E doctor - magic!
I also knew I couldn't go on as I had been and I made up my mind to start taking the Citalopram. Like you I was petrified of side effects, so I cut my first tablet into four. It was crumbs, but I put them on my tongue that first day and for the next three. Then I went up to half a tablet, and finally a full tablet.
Apart from the slightly spaced out feeling you describe and a loss of appetite (yeah I know ADs are supposed to make you put on weight!) I was just fine.
For three months I also took the Bisoprolol alongside but I soon realised I didn't need them. The anti-depressant had taken care of all the physical symptoms as well. My heart rate now is just normal. I don't feel myself thumping and vibrating any more. All that has stopped.
15 months on and I am a different person. Citalopram has changed my life. I take my tablet 20mg a day at lunchtime, and that's it. I'm happy, upbeat, anxiety free and content and I don't have any of those horrific physical symptoms I used to have.
Sometimes I think about coming off them, and maybe I will next year start scaling down, but at the moment they work for me. I'm slimmer and more active than I've ever been (and I know that weight gain is a concern for many on ADs, but for me personally it's had the opposite effect).
Give the Sertraline a chance. They will take time to work so don't give up too soon and any side effects will mitigate as your body gets used to them. If they really don't work for you then other ADs are available.
As many have said on this thread (and numerous others), these drugs really can be life changing. Give them an chance to work and if you have side effects and adverse reactions, then don't hesitate to go back to your GP and try alternatives.
Good luck and don't give up!