So this morning drove into work just fine no issues which is about a fifteen mile drive, back the truck in and everything was fine until I put the truck in park. The RPM went up from about 800 to 1,200 and sat there regardless if foot was on the break or not. Shut the truck off turned it back on a couple minutes later, truck stayed at around 1,200 RPM put it in drive pulled forward a bit, then put it in reverse truck shuttered a little bit and rpm dropped back to normal range. Any ideas as to what the problem could be? any help would be greatly appreciated.