The "Convenience" of not exercising

I don't want to come to a point where I conveniently "forgot" to exercise.  However, I did.  I meant to go on that mental schedule I was preparing myself.  Yep.  It was a sorry yet convenient excuse.  The truth is, I am a beginner who has no clue how to start.  Should I start strength training?  Walking?  Anything?  I for one am tempted to just do anything no matter how advanced just so I could push the limit.  I fear that I may quit or get bored after awhile.  I just don't want that.  I need help in overcoming my fears, so I wonder how to go about doing that.