I am a noob here, hope you don't mind me chiming in. I often get the same feelings as you, and for me, sometimes I think it's the idea of going out and having to go for "x" miles...what I try to do is tell myself, "OK, I'll just go for 30 mins, and if I want to come home, I will". 9 times out of 10 once I get out there and get going, I don't want to turn back.

Good luck and I hope that motivation comes back full force for you soon