When you get itchy when you lay in bed but no bugs are around it can be a result of a combination of factors that are related to your body's natural skin conditions and rhythms.
At night your body temperature also rises slightly, and you might also experience skin dryness or even hormonal shifts which can make you more sensitive to the itching that you feel at night when laying in bed.
Even some medications and mental health issues and bedding can result in itching when you lay in bed.
The body's natural sleep wake cycle or "circadian rhythm" can also cause your skin temperature to rise or increase slightly during the night which can also trigger itchiness.
And the shift in skin temperature can also be accompanied by a decrease in hormones which help to regulate inflammation, which can also make your skin more susceptible to itching.
And as your skin also loses moisture at night, the skin can also become dry and itchy, especially in dry climates or during winter.
Eczema and psoriasis and even contact dermatitis can also cause itchiness at night.
Eczema and psoriasis are inflammatory skin conditions which can cause intense itching, which can be worse at night.
And allergic reactions or irritations from detergents, fabrics or even body lotions can cause itching, especially if you're sensitive to certain materials.
Moisturizing your skin before you go to bed by using a thick fragrance free moisturize can help reduce the itchiness.