The LED should be either fully on or fully off. If it's not, assuming you've wired it correctly, then it would mean that the cell is not holding its charge properly - so it reaches 3.3, charge current stops, cell voltage quickly reduces to 3.1 (or whatever) which starts it up again. If you have a CRO, you can check if there's an oscillation on the LED, or if no CRO, connect a speaker/earphone across the LED and you should be able to hear the oscillation...depending on how good your hearing is.
Actually, if you connect a capacitor across the 1.8M resistor, maybe 1-10uf, if oscillation is the problem, then the LED will visibly flash. (i think)