My body temp was 101.5 and I had sweating and heart palpitations 1.5 months after epidural steroid injection with 8 year history of Zoloft (sertraline) use. Is this serotonin syndrome?

No. We doctors have a saying: "when you hear hoofbeats, don't think of zebras." in other words, common things occur much more commonly than rare things. Serotonin syndrome is rare, and typically occurs immediately after taking a drug, not 1.5 months later. The most likely cause of a fever and palpitations is a viral illness. Let your doctor examine you, to put your mind at ease.
Probably not. This is probably not serotonin syndrome. But with all the difficulties people have had with epidural steroid injections recently, you do need to be seen by a physician very soon -- even emergently. That is, unless what you're describing is something that happened in the past, is now resolved, and you're now well with no symptoms.
Emergency. You need evaluation by physician. Consider going to emergency room.