[low ufo]

My car has just started smokeing on the right side on start up when its been warmed up. It appears to only do this only on start up for a second or so.and a couple of times today when I was at idle at a light and took off I noticed a cloud of blue smoke behind me !!!!! I thought this can,t be me ! Must be the guy in the beater vega . But in fact it was. I don,t beat the car at all,it seems to run fine.I,m thinking valve guide ?? when started cold no smoke, also yesterday I was parked for 1/2 hour on a slight grade rear end up.when I started the car this was the first time I noticed smoke ( A large cloud ).Eng. 428 Fe with elder. heads.Question :what should I check 1st etc.
thanx for all your advise in advance !
Mike