Elantra automatically sometimes doesn't jump fourth gear.

Neutral d can't move. If the cause of brake sticking is ruled out, it should be caused by the low working efficiency of hydraulic torque converter, which is related to oil temperature, oil product and oil pressure. There are many reasons why you can't jump to the fourth gear, such as sliding friction plate, the fourth gear solenoid valve not working, hydraulic valve failure, oil circuit blockage, solenoid valve circuit and so on. But today you are back to normal, which means it may just be an accidental failure. Keep watching. Automatic transmission, keeping the oil pure is the key.

Don't take it lightly, the variable timing solenoid valve is faulty. Incorrect valve timing, poor combustion quality, and great damage to the engine (carbon deposition, oil consumption, substandard emissions, and insufficient power). It must be repaired as soon as possible.