Sounds like you had a panic attack, but Nicotine overdose can cause lightheadedness, cold extremities (hands and fingers), ringing in the ears, dizziness, rapid heartbeat, and a cold sweat. Were you a former smoker or are you a non-smoker who tried
vaping?
What strength are you
vaping? You said 6ml in your post, but that's a liquid quantity. Nicotine content is usually expressed as milligram per milliliter (as in 24mg/ml). I started at 24mg/ml at first and never had nic overdose effects, but I was a 2 PAD smoker. 18mg/ml is a common starting point for most smokers.
If you happen to be a non-smoker who wanted to try
vaping, a good nicotine starting point in your juice would be 3mg/ml or no more than 6mg/ml. Since you stopped for a year before vaping you need low nicotine or maybe even no nic to start, especially if you are vaping on a cloud atomizer, direct to lung high, airflow mod. If you can breathe easily through the atomizer it's a DTL device and you get a lot of nic at one time.
Since you haven't smoked for a year even a little nic can cause the symptoms you described, but you should get checked out by a doctor. What you described could be nic overdose or a just a panic attack, or a combination of both, but until you are diagnosed by an MD all bets are off.
Blacking out can also be a heart rhythm issue, so go have a checkout with an EKG and blood work and find out if you are having skipped heartbeats or something else. If a doctor checks you out it will also give you confidence that it's likely nothing serious.
I'm no doctor, but when I was younger I had similar symptoms once or twice. Getting checked out boosted my confidence that it was a transient occurrence brought on by stress.