Dizziness And Heavy Sweating Suddenly Appear At Of No Where.

Dizziness and heavy sweating suddenly appear at of no where. What use to happen a couple of times each year is now increasing in frequency. Usually goes for 10-15 minutes then I cool down and come back to normal. The only thing that is the same seems to be standing, warm conditions. Sometimes I'm relaxed, other times I'm a little more stressed. Stretching my arms out for a period of time seems to bring on problem, never do I lock my legs in anyway. I have fainted several times because I didn't sit down in time. No chest pains, I actually had a right kidney pain this time, first time I have felt anything like this. I was diagnosed with a kidney stone in left kidney 5 months ago, very small but caused some uncomfort. The fainting spells started years ago, stones just recently. Blood pressure sometimes high and sometimes normal. 15 lbs. overweight. Have a military neck (according to chiropractor) could this be a concern? I have terrible eating times and habits.