S5 xenon head light issue

Morning guys, any ideas on this please?
08 S5, one headlamp went out last night, got the dash warning. I'm not overly surprised, as the other bulb blew in the spring, so only around 60 night time driving hours since. But. Upon ignition restart, it flickers then works for a few minutes, before going out again!? Does that indicate the bulb ok but another issue?
turning head lights off then on again doesn't relight it, needs an ignition restart.
i know the bulbs are bloody expensive... But at least have the TPS part number now after the other one went.
many thanks in advance!