I have been doing a 4 day split routine, where I work my total body twice a week, for about 6 months now. I have been losing my motivation lately to go to the gym. I was wondering if perhaps I am doing too much work? Could I be overtraining? I have seen many other peoples routines, and it seems that the majority work their whole body only once a week. I will generally do about 5 working sets after warm-up for my larger muscle groups (usually the last 2 to failure), and around 3 for my smaller body parts.

I would love to work my whole body only once a week, as this would cut the amount of time that I am in the gym down to roughly half. But at the same time, this just doesn't seem like enough work. Can anyone give some advice here? (I am eating healthy, and I generally get around 9 hours of sleep per night.)

A lack of motivation can be a sign of overtraining. Are you seeing any othr signs of staleness, e.g., sleep disturbance, or lack of appetite, increased muscle soreness?

Don't be afraid to take a week off, and allow your body to rest. You will go back even stronger. I am in the middle of an 8-day layoff right now - a pre-emptive measure against overtraining. I avoid going stir-crazy by taking some light cardio workout classes and going swimming. My first 1-2 times back on the weights will be relatively light and then back with a vengeance for another 6-7 weeks.

Try not lifting to failure. For me, lifting to failure more than once a week, leads to overtraining. Or lift only once a week.

Maybe you can try and change your workout routine. I try to do it every 6-8 weeks so i dont get bored doing the same thing again and again.
One week rest is definately a good point. Take a break but keep a check on your food intake..

Good Luck !