Is it an iPhone 4, 4S, 5 or 5S ?
It's possible you reached the end of your battery life cycle.
How long ago did you jailbreak it ?
Did it work for some time, or did the battery issue began exactly after the jailbreak ?
Have you added any hacks that might cause boot loop ?
Did you try charging it on wall charger overnight ?
Non-jailbroken iPhone 5 battery issues (not sure what model you have)