My car keeps shutting down.

Hi, I dont speak english natively so ill try to be as
clear as possible. Its a kompressor c230 coupe,
tiptronic 2003. A few weeks ago the car started
failing. When driving up a hill the gear(gearbox)
didnt change. Even when pushing full on the gas (it
sounded as if it was forced, but it didnt change),
after reaching the hill, it worked fine. Lately it
happens more and it happens even when Im not up
a hill (like in a stop sign) theres some delay in the
gear, sounds like forced for a few seconds and
then the gear change (I also tried shutting down
the engine, then I turn it on again and changing the
gear from drive to reverse few times. It helped a
couple of times, but surely didnt fix it). Today it
didnt showed any issue, but when leaving work, I
turn the engine on and it only lasted on for around
3 secs then it shutted down again (this happened
several times). I was not able to fix it. Had to take a
taxi back home.

I will kindly appreciate any help and will answer any
question if needed. Thanks you all in advance.