Please ... I need help. My car is showing the jellow triangle sign and the message to stop the car and put the transmission on "P" leave the vehicle and

go find a mechanic. The problem is that the sign and message appear only for a few seconds and dissapear without a trace. It happens few times a day 

and sometimes not for days.

Has enyone experienced the same?

You need to scan the module for any stored fault codes.

Sounds a bit like this thread, have a read.