I am not sure what you mean by palpitations. Do you mean you feel your beat is rapid or that it is beating oddly? If it is beating oddly it may be due to a slower heart rate. Smoking speeds up your heart rate so you likely staved off or didn't feel an irregular beat when you may have still had it but now since it is a bit slower it is a bit more pronounced. I would say visit a doctor to get evaluated if you haven't already considering you have a history of smoking. If your heart is deemed structurally normal and free from disease then the odd beats are nothing to worry about. If you are having a rapid beat then the doctor will address that as well but more than likely you have nothing to worry about but it is best you have a doctor decide that. That said, the heart is strong and can handle a lot but it can also be very slow to recover so you heart may be recovering from all the smoking and may take some time maybe even up to a good year to get to its health back but it is likely with a bit of distance you will stop noticing the odd beats for some they go away but either way if your heart is deemed healthy you have nothing to worry about. Your best bet regardless of the odd beats is to stay away from the smoking. Regardless if it makes you feel physically better in the short term in the long run you will likely have more major more troubling health problems if you went back into the habit so try to stay strong and the odd beats won't control your life. Take care and if you have any more questions let us know but do go and get checked out just to get a base line.