Q: Independently decelerating until car stalls when driving greater than 40 mph. Plus there is high RPM's with acceleration and won't always start in the mornings.

Niece's car and this is her report of trouble and work done: Beginning 1 year ago in the winter of 2015/16, occasionally car would independently decelerate until stalled at 40 mph or faster. After letting car sit about a minute, it would restart and be drivable again. July '16 she had 4 motor/transmission mounts, transmission thermostat, water pump, and water outlet gasket replaced. Car ran well for 1-2 months until same symptoms returned, plus high RPMs when accelerating, and sometimes car not starting in the mornings. However, car would always start later in the day. In Sep '16, head mounts were replaced and transmission flushed. Symptoms were gone again but for only one month this time. All symptoms returned late Oct '16. Car will not always start later in the day anymore, so that symptom has worsened. What is causing this? Is it the same issue causing all these problems?

Thank you for any information or help you can offer! Amy and niece in Michigan

Her car has 180000 miles.
Her car has an automatic transmission.