My Husband Experiences Episodes Of Sweating, Clammy Skin, Nausea, Lightheadedness

My husband experiences episodes of sweating, clammy skin, nausea, lightheadedness and weakness periodically. He has to sit down and be calm until it passes - which is usually about 5 + minutes. He slowly comes out of it, and within 10-15 minutes, he is totally OK.
This has happened about 5 times in the past 6-8 months

He is not overweight; he eats very healthy foods; and he is an avid swimmer.
His father had bad heart issues - stints; triple bypass; etc. His father was also diabetic.

My husband had a shoulder replacement a year ago, and the first night and the next morning he was home after the surgery, he passed out and I thought he died - twice. His doctor said it was not all that uncommon for this to happen - he actually had a name for it, but I can't remember what it was. He explained that it had to do with blood pressure and coming off the drugs. I only bring this up because he sweated profusely when those two episodes happened as well