Car froze at 40 mph accelerator to the floor & did not respond to brake pedal

What is your question?

Car is at 99200 miles, Hyundai Elantra 2013 From 88000 miles the car has on occasion at 30-40 mph, RPMs race, the car loses acceleration, recatches and drives normal (no codes). At 99,000 the car coded P0304 4th piston misfire. Tune-up and fuel induction service done 2 weeks ago at 99,000. Car did the previous "hiccup" twice in the last 2 weeks and then on Friday my 16 year old was driving by herself and the car froze at 40 mph. The car would not go faster or slower than 40mph for maybe a few seconds. The car did not respond to the accelerator to the floor and she tried the brake with no response, then the car drove normally. HELP The car has once again become unsafe (traction sensor failed at 56,000 miles) but I knew how to turn traction off when the car locked up at 50mph

What makes this problem better or worse?

Just driving, no known conditions

How long has your 2013 Hyundai Elantra had this problem?

88,000-99,200 miles 3 oil changes