2005 Nissan Altima A wired shock!!

I have a 2005 nissan altima, Some times when i leave it parked outside, where the temperature is a bit high, upon starting the car, the engine light turns on and the rev meter gets limited to 2500 rpms, secondly if i drive it in this condition there is a huge wired shock when it shifts to second gear. And the rev remains limited to 2500 rpms. After driving in this condition for 5-10 minutes, if i turn the engine off and start it again, the light disappears and sometime it stays. I really can't figure out the matter. I have consulted mechanics. some say the problem is with the gear box others say its with the engine mountings. can u please shed some light on the problem..