Hi guys got a couple of little niggles with Bertha, nothing major but do need sorting but i'm baffled with them

when she's been turned over first time she runs rough like she's missing if i run her up to the local shop (2 minute drive) and try starting her again she fires up then dies straight away, takes a few minutes of turning over with accelerator depressed to get her running again and for a few minutes she lacks power and misses, now i've replaced the ht leads and plugs thinking it may be that but she still has this problem, any ideas what these problems could be? when she's warm she usually runs perfect, did a 80 mile round trip yesterday without fault when she warmed up,

thanks in advance
Rob

poss hg failure water settling in bore after standing all night clears when spark plug comes back to life,take plugs out 1 by 1 if you have 1 looking like brand new this is the problem cylinder