Hmmmm, no, it is definitely a side effect from the Zoloft. I had something similar when I first started or was on too high a dose.

I literally didn't sleep for the first few days I was taking it, and during the day, I was jittery. Also, tired a lot. For me, as long as I was under 100mg, the jittery was managable unless I had caffiene or something else that threw off my balance. If you can, you might want to wait a week or so to see if it goes away. If it doesn't and it's unbearable, you might want to switch. Taking Valium to counteract the jitteriness is not a sustainable solution. You will build up a tolerance and become dependent on that if you use daily for long enough. You might also want to know that Zoloft can cause anxiety to develop in some patients.