limp mode tdi pd130

After having put right several expensive faults on my car i now have another headache to sort out, It all started this afternoon when the car would turn over but not start (never heard the fuel pump noise) after reading on here i managed to get it started and get back home. On the way home it was running in limp mode, i now have the issue of starting the car (sometimes it will / sometimes it wont) and it is in limp mode constantly (even if i switch off and back on). Any suggestion on what it could be ?? i dont have a VAGcom atm