no start then start

My 89 190E 2.6 has been acting ugly lately. It's been starting from cold fine, drive across town less than 2 miles, turn it off, go into a store for about 20 minutes, then the car won't start. Wait for about an hour and it will start again.
Today, it would not start from cold. I took out the FP relay and beat it on the fender, reinstalled it and it started. Should I replace it just to be safe?

Yesterday while waiting in line at Captain D's drive through, the car started sputtering and almost stalled...I left the line and hit the road again...it sputtered a couple more times and then took off fine. I put in new plugs after that thinking it may be misfiring. Next probably need to check the distributor...don't know how old it is. Any other thoughts?