1998 bmw 528I runs ruff after starting,smooths out after 30 sec.

Hi can you check the engine oil please and get back to me thanks.

Have you tried disconnecting the hot wire from the battery to the starter and cleaning both the connection from battery and on the starter. A toothbrush and water/baking soda?

Try cleaning or replacing air mass flow sensor... (or clean but a dirty one usually results in car running unsmooth. not, not starting.. hope this helps... Craig

your diagnosis would seem to be correct. when a head gasket goes, coolant can leak into the combustion chamber where the coolant turns to steam and vents to the exhaust.

an air lock in the system.that is what the bleeders for...

ruff idle may b idle controll senc. ----tapping may be plugs-- wires, and or gas try 91 oct gas next 3 tanks and see thats the cheeepset place to start

batterys in the remote??

replace relays and fuses for the power seat and windows.change dash light bulbs.if bulbs are good you got wiring problem check ground wires.

If you've never replaced the timing belt or chain,That would be my first thing I'd check is the Timing belt or chai, just aline the timing marks on crankshaft and then look at the position on the distributor to see if it's pointed in the #1 firing position .

telemachas is totally correct with this type of car,also when pulling one of these engines apart i also found a lot of wear on the piston ring groves ,although rings were good the pistons themselves needed renewing .This would cause oil to be pumped into combustion chambers on initial start up.Problem was the cost of parts was more than the car was worth so customer bought another car as this one had been inported from germany and was so rusty as well it was just a scrapper and worst of all it had no air con