Why won't car go??

What is your question?

I just got a Honda accord EX-L V6(122,000) about 6 months ago, The car will just stop driving, it still accelerates(PPM) still goes up. The first time it happened I was at a red light waiting. This time (2nd time) I was exiting my neighborhood doing about 40 with the rpm at 4-5 When it just stopped going but still accelerating. The first time it happened we got a tow truck to take it home and i didn't start it til my mechanic came to my house, surprisingly it started working outta nowhere, Also an important detail is if i put in park it makes a horrible grinding noise.

What makes this problem better or worse?

Problem happens outta nowhere

How long has your 2008 Honda Accord had this problem?

A rare occurance