Is this my gearbox???
 

Hi all,will try to describe what actually happened:
I started and moved gear from P to R,accelerated but absolutely nothing happened for the first few seconds,then slowly car moved back,kept rolling for another few seconds then finally jolted and everything was fine suddenly...:confused:
Same thing happened before while driving slowly on a parking lot,just lost power,did not respond to acceleration for a few seconds,again jolted and back to normal...
I'm very worried it may be my gearbox as the repair cost will be beyond my budget...
Have you any ideas what it is?Thanks in advance guys
Audi A6 1.8T petrol/automatic