Cars rpm goes up while I'm driving, but my speed stays the same speed

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My car rpms will jump up while I'm driving. Does not go any faster stays the same speed I'm driving. Also a new symptom it happened twice after shutting it off. Acted like it did not want to start, like it was not getting gas; though, I was pushing on the peddle it seemed like it had no gas to it. It will usually start right up with out using my pedal I just turn my key. but this time it did not to start, so I pumped it a few times waited about ten minute and it started right up no engine light took it to tranny dealer he said he could not figure out what was wrong with it by his computer machine he said if and when it has new symptom bring it back. well the new symptom is it not wanting to just start up. any ideas and the rpm thing is still happening.