Weird starting problem

Ok, so I was at my buddies house the other night. I went out to start my 97 GS-T and it was like 15-20 below 0f without the wind chill. I tried turning it over but it would only fire once in a while. I hooked jumper cables up thinking that it wasn't turning fast enough but it still wouldn't start. I left it there for the night and came back the next day and it was like 15 above then and it still just poped once in a while. So we but it in his garage and set the bullet heater facing it. The garage was warmed up to about 50deg. for a while and still nothing. So we moved it out to his shed and i was going to come pick it up later. His dad went out a few days later and tried to start it and it started right up. He let it idle for about 15-20 minuets and them i came. I shut it off once and turned it back on right away and it started faster that it ever had scince I have owned the car. I did it again and started just the same. Then i did it a third time and then it wouldn't idle without dieing but it still started. I left it for the day and drove it home that night with it starting and driving just fine. It's been sitting at my house ever sence then because I havn't had a chance to look at it. Any suggestions.