1995 Pontiac Trans Am PROBLEMS

Need to see if anyone has any suggestions for this. I have read through countless email and can't find anything with similar enough symtoms. I have a 1995 5.7L V8 6speed manual TA with 145k mi. I have had very little problems with this car and with the exception of a water pump and plugs, wires, etc have had to replace nothing. This one has me pretty stumped. Has been hard starting for a while and when it does start it starts kinds half hearted(used to start instantly and "VROOMMM"). A while back, starting became less, for lack of a better word, powerful. Kinda weak starting I guess. After a while of this, it started to perform poorly after driving it somewhere, getting it up to temp, and turning it off. Would go into a store, come out 10 min later and It started fine but when I started driving it was real jerky like it was missing or running out of gas. It would do this for about a mile then it was fine. As long as it sat for a few hours and cooled off completely, it didnt do this next time I drove it. I dont drive it but once a week if that. Now car barely starts if at all. If it does start, it runs fine as long as you don't turn it off and as long as it had been sitting for a while. If you turn it off once up to temp it wont start at all or if it does once you start off it dies and won't run or restart again. Unless it sits for a few hours. I drove it 4 hours from a cold start a few weeks ago and it ran great the whole way, turned it off and it was done, wouldn't idle wouldn't run. Then got in it a few days later and it started. What has me stumped is why, if it starts cold and if it starts, I can drive it as long as I want without turning it off and it runs great. Soon as you turn it off and try to restart while still warm it doesnt want any part of it. Most of what I have read consists of stalling while running not this. Anyone had any experience with this? Any suggestions? I really can afford to take it in and start the expensive trial and error thing at the shop so thought I would see if anyone has experienced this and what it might be.