Is it possible 2get a bit of increased anxiety & agitation after first 4weeks on zoloft (sertraline)? i've had a few heart palps too, does that mean its dangerous?

It is possible: It can cause an initial increase in anxiety, but after 4 weeks, that should go away and anxiety should decrease. Some people have paradoxical responses and become more anxious, which may mean it is not the best drug for you. Worst case, the drug could precipitate a manic episode in someone with undiagnosed bipolar disorder. Have a discussion with your doctor to discuss your treatment options.

Possible but doubt?: If you have been on only 12.5 mg of zoloft (sertraline) for 4 weeks you have not been dosed correctly. Also with cold sensitivity has your thyroid been checked? Even if the TSH is normal, take your axial temp morn, afternoon, even, and hs for 7-14 days. If the temp if.