Hi,
The symptom itself (steering wheel stuck for a second) is most probably caused by the EPS ecu, which temporarily goes to a fail-safe state and restarts itself. Normally, upon a power shortage, you would more likely feel the steering support goes lower and lower before it cuts out completely - but i am talking about EPS systems in general, i am not familiar with this particular model. Maybe it ts too old and simple for that.
Like the others said, it can be some power supply related problem, but it must be some kind that it shuts down the system immediately. The fact the EPS light does not lit up also assumes that the ecu does not have time to show error indication, but it restarts itself immediately and then it thinks that everything is recovered.
Normally the symptom could be also caused by the overheating of the steering system, but since you said it is gone after 2-4 times, it makes it less probable.
So, first of all, I recommend to check and clean the electrical connection of the ecu, as it really needs tons of power ( > 100A ) when you are steering a standing vehicle. It is sealed well and it is unlikely to corrode, but you never know...
And, i would really try another battery, even if it looks fine otherwise. Maybe a borrowed one.
If it not helps, and you want to start debugging it, it would be great if you could measure the voltage and/or the power consumption during the occurrence of the fault. Unfortunately, you will need some fast measurement solution, like an oscilloscope. You can use special insulation-piercing probes for simplicity. Then, you can see then how much does the battery voltage drop at the ecu (during steering), and see if it drops lower when the fault occurs. If the voltage considerably drops, it indicates some external problem: cables, connectors, or battery (to rule out the problem with the battery, you can paralelly check the voltage on the battery and near the ecu). If the voltage looks fine, it is unfortunately some internal ecu error. You can try to disassemble it and re-solder what you can, but it is more likely you will need to replace it.