Z4 Shuddering at idle

[erdnase]

I haven't used my 2003 2.5 Z4 for 3 days or so - it's been sat outside. Today I went out to run the engine for 5 or 10 mins, just to keep things smooth and ticking over, and upon starting I noticed a shuddering. It lasted 20 seconds or so, and never re-appeared for the whole 10 mins I was letting the engine idle over.

I've never experienced anything like this, and it worried me a little. No warning lights came on, and everything else is working fine. A quick google suggests it's quite normal, especially after a few days of sitting parked up. Is there anything I should be worried about? I'm taking it in for an MOT tomorrow, so if there's anything that may be causing this (assuming it's not normal), I can have them take a look at the same time.

Thanks in advance!

[JimexPL]

My 3.0 did it occasionally over the 25,000 miles that I had it, as have many other modern cars that I've had access to over the years.

In some cars low battery voltage can be the cause - perhaps get yours checked before the winter?

Wouldn't worry about it. It's almost as if the ecu gets caught napping and forgets how to run smoothly!