central heat wont stay running ?

I recently tried starting my central heating unit it failed to start i have made several attempts to get it going when i removed the blower door on the bottom of the unit it seemed like it wanted to start but only tried very briefly and then shut back off i can press and release the safety swtich and sometimes it will try to come on and then it will shut back off and the next time it wont even act like its trying too come on please help i have a 13 month old in the home and its going too be very cold tonite thanks