Feeling weird after elliptical?

Last night at the gym I used the elliptical...I was going to go for 30 minutes, and normally I am fine, but last night was just weird. At 20 minutes I started to feel tired, but I figured that I had 10 more minutes left...4 of which were a cool down, I could handle it...I slowed down a little but not too much...and I wasn't going too fast to start with either. At 23 minutes I had a wave of exhaustion pass over me and it felt so hard to just move my legs. I tried to go for a little longer but I only got another 30 seconds in before I KNEW I had to stop...I could tell something wasn't right. I didn't feel sick, but I felt cold..like when you have a fever...I also felt slightly light headed...not dizzy just like something wasn't right. I don't have any problems with sleep deprivation or anything...normally 8-9 hours a night, I had eaten enough yesterday so it wasn't a lack of calories, and I drank a lot of water throughout the day. When I got home I went straight to sleep, and normally I am up an hour or so after I get home so that was weird too. Any idea's what was wrong?

I bet that you're just coming down with something.  Give it a few days and see how you feel next time. 

That happened to me once. I do the elliptical a few times a week and usually really attack it...but one time, I felt like I could barely catch my breath at half the normal speed, and didn't have an ounce of strength left after about 15 minutes. I think for me, my body just needed a break. So much stress at work, trying to work out several days a week...I was just getting run down. Like the last poster suggested, your immune system is trying to tell you something. Take a couple days off.

well the next day I felt fine...but I was really tired that night so I didn't go to the gym....I think I fell asleep at like 8:30 which isn't normal....then last night I went on the elliptical again and went for 40 minutes and I really attacked it and I was fine...so who knows!

dehydration

Dehydration and/or nutrient deficiency (i.e. you didn't have enough energy).  If I do cardio when I haven't eaten enough this happens to me.