car rpm goes really low when switching gears from P to R

[brigon19]

i had the car for a lil over a month. since i bough it when swiching from P to R the to R to N and so on . i notice that the rmp go way down like if the was car was to stall .( it has died a few times. i check that i have to air leak.and its fine. also compression is fine too. its just happens when i change gear. also there's no check light. i had the check light twice for about 10 to 15 second the it turns of again and dont actually get a check light.