Start by clearing out your internet cache files.
If the cache area is full, your PC needs to clear off old files before storing new files.
For that matter, check how much free hard drive space you have.
I get very nervous when I have less than 1GB of free hard drive space.
Next, it may be time to remove and re-install IE (or whatever browser you are using)
When the PC reboots, it usually means that a file is corrupt.
With W98, another tool that you have is System File Checker.
Fromthe run box, type in and run sfc
Check all files for corrupt and out of date files.
Be cautios about replacing a file that is a newer version than the one in the database.
Many files have been updated over the last 4 years.
Beyond that, you may have a memory leak, bad RAM, or too much RAM.
Windows 98 does have a bug where if you have more than 511MB of RAM installed, strange problems can crop up.
Chas