Jitters are pretty much an individual response based on dose, food intake, coffee added, caffeine/stimulant tolerance, etc. but generally speaking you should acclimate in a few days. Most ECA instructions would tell new users to ramp up dosage to see how their body reacts.
My first experience was jitters and increased temp that lasted 4-6 hours and faded until I took it again the next day. By the end of the week I was fine and bumped the dose up.