NHTSA Complaint #11656826 — 2008 HYUNDAI SONATA

Bought in 2023 @ 98k miles. Have had trouble with 1.it would only start in drive, then that seems to have self corrected. 2. In drive, car would not accelerate properly, and would slow as though I was braking, but no foot on brake. Had rear brake sensor replaced, seemed better for a while. 3. Developed oil leak at 120 miles which valvoline characterized as "not serious...just keep checking it and topping it off." So, have been doing that. Today after oil change, it began running rough, lots of vibration, then the shifting problem, sluggishness, and new..smoke from under hood on driver's side. No check engine lights at all. Nothing registered as hot or overheating. Turned off car, checked oil and trans fluid, both in proper range for warm engine. Let car sit and cool for an hour. Decided I had parked too close to the propane tanks for a smoking car, so I decided to start car just to back it into a space across the lot. Car had no issues- No smoke, no jerking or vibration, no sluggishness, no phantom braking. This car has done this same thing about once every 6 months since I've had it. Changed a tire sensor, that seemed to fix it once. Stopped using cruise control altogether, that seemed to help once. My brother is an ASE certified high school auto mechanics teacher who ran his own shop for 20 years and worked on trucks for VDOT for another 7 years and he cannot diagnose it. I know it has something to do with not being in the correct gear, but it's not reliable, and I have a hard time believing it's just my vehicle.