Can't seem to keep my motivation!

[Tripper11]

I hate this mind fuck I am putting myself through! I recently gained some weight and so I joined a gym to try and obviously get myself back into some kind of shape as the shape round doesn't work for me.
I have gone maybe once a week in the last month. Of course once I get there and start up I am fine and of course I feel good after having gone, but I just can't seem to get into a habit of it.
I know what I need to do, but I keep having these stupid internal arguments with myself, talking myself out of going. Too cold, too tired, maybe later, etc etc etc.
I have noticed how my clothes are not comfortable anymore and I find it easier, which it is, to just go and take a nap instead, or just casually putter around the house doing inane things that are not very important at all.

So, aside from just laying out a little rant about my lack of motivation here, I guess I'm asking for a little advice on what I can do to get my motivation up and begin a routine that will stick.