I've seen this happen too many times, and I've done that to myself. Well I decide to exercise, but I jump in all the way, exercising 6times a week. Then after a month I quit, because I got burnt out.
This is a life style change after all, to keep the weight off after we have lost it. We will have to continue exercising in some sort of way. So I recommend this:
1. Start out 2times a week cardio (30-60min+) 2-3 weeks, plus being concious about walking more in general (parking farther, swimming, playing with kids,etc)
2. Then 3times a week cardio (30-60min+) for 2-3weeks, plus being conciously active the rest of the time in between.
3. 3times a week cardio, and 2times a week strength training (30minutes). Plus being conciously active.
Not only will this help fight burnt out blues, this will keep your body guessing while progressing.
Then what you will want to do, to keep progressing is increase intensity, and time working out as you go along.
I.e. 30min strength training add additional 15 minutes.
Progressing and setting goals for myself as I go along has kept me motivated, and interested as well.
So my friends, keep progressing and don't get burnt. That is my hope for us all.