I have a Mercedes c220 1995 my turning signals sometimes work sometimes not

most likely a bad switch, the turn signal lever/stalk is the switch for all three functions, wiper, wash, turn signal.

Check fuse and relay.

check for water damage inside the light (circuit board)

first check out your fuse.....may be it is broken

see if this link helps.
Turn signals not working in my 1984 mercedes benz 190E Google Search

first check signal lights fuses if none of signal lights work.if fuse okay,check for burn out bulbs.if all is good turn signal switch is bad or you have loose wire to signal switch if your turn signal lights work some times.

replace flasher unit. Under hood, driver side, upper firewall, mounted in corner of engine compartment

i have a Mercedes Benz C200 Kompressor , I just changed the plugs, air filter and oil filter and put new oil, but it's now miss firing badly can some one out there help?

Barrel fuses used to be made of aluminum and corrode on the copper contacts. Pull fuses and replace. 10-15 dollars now will help get rid of electrical gremlins.

your control switch is faulty on the steering column