Welcome back! It's great that you want to stop yourself now and get back to a healthier you. Unfortunately it takes a lot more than motivation. If there's one thing I've learned from the people on this site who have been successful at losing a lot of weight &
keeping it off it's this: commitment.
It takes a decision to commit to this lifestyle. Yes, there are times when it may be "forced", but if you've made that commitment then you're much more likely to follow through with a plan than if you're just waiting to be motivated.
There are things that may help you to reaffirm your commitment. Lots of people cite pictures of themselves, logs of their weight loss, old clothes etc as things they look at when they fear they're losing their way. I'm not so sure they motivate as they do remind us of why we're doing this forever. (Although I'm sure they motivate some! But maybe not as much we hope all the time.)
Do you have items like this? Maybe taking a look through them will remind you.
So now... You've let your gym membership lapse, hate your stair stepper and don't want to walk in the cold. You know you have to do something, and while it's great to be moving at all, you shouldn't have to hate it. Did you like your gym? Get your membership up to date. You'll have more work out options (maybe even some classes!) and it won't be walking outdoors

Don't "set yourself up to fail" by closing doors to exercise.
About the food. You'll be less likely to eat treats if there aren't any around. Keep them away from you as best you can. "Out of sight, out of mind. Out of house, out of mouth."
Just know that you CAN do this!

You have it in you to keep going and to succeed! We're all rooting for you ^^