There is a fairly common RAM issue with the T30 models that causes the RAM sockets to come unsoldered from the motherboard over time, which would basically disconnect the modules from the computer over time.
The easiest way to get around this is to just replace the motherboard entirely, but if you are more skilled with soldering, then it is an option to just resolder the pins from the RAM slot to the motherboard. There is some helpful information [https://forum.thinkpads.com/viewtopic.php?t=92000|on the ThinkPad forum here] that you may find a good read within.
Good luck!