Surging problem?

I have written about this vehicle before in regard to the clutch. That is fine. I have not driven this Nissan very much in the last two months but have only driven a little and start it about once a week. Drove it today after sitting maybe 2 weeks. Drove about 2 miles. No problem. I came back after 5 minutes and didn't get out of the parking lot before I noticed a very dramatic drop in power. Pressing the gas pedal was mostly doing nothing except a rise in RPMs/power randomly and not very often. Check engine did come on. Was Steady, never blinking. I pulled over and checked under the hood. All seemed normal visually. I opened the radiator cap some because I noticed it wasn't hot at all. The cap that is. Forgot to feel hoses. Anyway, I heard a decent burst of air come out before I had to close the cap to avoid 3rd degree burns possibly. Got back in the vehicle and decided to drive some more and it seemed to be better, I am thinking okay that fixed it. Even check engine light turned off. But alas, it only lasted a very short time before the same issue. Drove home the 2 miles extremely slow. From 1st gear, and 2nd acted the same. Very uninterested in giving me power, RPMs, or speed. Just trudged home for the most part. At one time it gave me a burst, check engine went off again, but back to its foolish ways. Checked engine oil when I got home, but it had not sat at all. Checked immediately and appeared low as in hmmm am I like really low on oil? It has never leaked before, and the oil is only about 5 months old. Will confirm oil level tomorrow as Colorado is freaking snowing.
I doubt it's a vacuum. Don't think it's the fuel pump. Thats decently new. Maybe there is air in coolant and or low. That's my thoughts anyway not sure how to bleed it. Could be oil. A sensor maybe? But it's mostly sat for 2 months and before that I drove it fine for 4 months. Hmmm, call up your mechanical senses and please help a brother out. I had literally no joke, just listed it for sale at $2,400.00 and had 8 people interested in an hour and 17 people in 2 hours. All of them Spanish hilariously enough. I'm Spanish so I can say that. So yeah, drove it to warm it up and because I'm about to get full price for this baby, and then Bam! Freaking life craps on my head. Dear God! Thanks man