The most likely cause, in this order: tire balance, tire out of round, wheel out of round, CV joint binding, drive shaft binding.
Tire pressure won't be the cause of a vibration, but might cause harder ride or softer ride, also pulling if the left or the right tire pressure is substantially different.
Tire pressure won't be the cause of a vibration, but might cause harder ride or softer ride, also pulling if the left or the right tire pressure is substantially different.